vol. 1
Mono Masters
(1955 to 1958)
vol. 2
Peak Contemporary
(1958 to 1966)
vol. 3
Tone Changes
(1966 to 1984)
vol. 4
Idiosyncrasies of the Sound (1984+)
It’s about building an illusion.
Creatures have been combining two channels into a single “soundstage” for millions of years. This is, after all, how most of us hear the world. You know those two satellite dishes on the sides of your head? Those are microphones, and they’re feeding signal to the studio monitors in your brain.
Evolution gave you tools like these for ultra-precise perception of sonic time and depth. Why, though? To hunt creatures in the wild? To avoid being hunted yourself? Whatever it was, two-channel audio reproduction was introduced to take advantage of that biology and trick us into thinking something that isn’t real, is. And that’s cool.
On a technical level, iterating a single-channel physical medium to suddenly hold two channels of sound presents several challenges. How do you double information without doubling size? How do you place two channels in close physical proximity without their signals blurring into one another?
The original phonograph disc was mono. Regardless of material or speed, the physics of monaural phonograph discs remain principally unchanged: etched grooves move laterally side to side on the surface of the disc, vibrating a pick up stylus, creating a single channel of sound.
Okay, now think of the three axes of three-dimensional physical space and superimpose them to an instantaneous moment in a monaural record groove. If you’re looking straight at the front of the playback cartridge, movement to the left and right is lateral action (the mono musical signal). The only other consideration is then movement along the groove with angular velocity equal to whatever speed the turntable is spinning at.
That accounts for two physical axes. What about the third? Therein lies the opportunity.
In the 1930s, engineers on both sides of the Atlantic attempted to use movement into and out of the disk surface (ie. vertical velocity) to pack another channel of sound into this singular groove— creating two-channel phonograph recordings. Those pioneers documented their success⁽¹⁾⁽²⁾ but the world wasn’t exactly ready; invention is one thing and commercial viability another. The two-channel phonograph disc didn’t become a consumer reality for another two decades.
But when the music industry finally opened the door, the specifics of groove geometry remained in question. Two camps emerged: one which promoted the “lateral-vertical” method, giving the lateral plane of movement entirely to one channel and vertical movement to the other; and a second camp which promoted “45/45” geometry, taking that L-V coil arrangement and turning it 45 degrees. This latter 45/45 system kept the two coils in perpendicular arrangement but angled both 45 degrees relative to the disc surface.
Two systems of stereo disc were demonstrated during show week—London privately and Westrex at a session of the AES Convention. The former uses a combination of vertical and lateral recording, while the latter uses a combination of two hill-and-dale recordings, one on each face of the conventional 90 deg. groove. Both are said to be compatible* and were so demonstrated…
— Audio Magazine, Editor’s Review, November 1957 ⁽³⁾
*this was basically a lie, unless a consumer’s mono cart had vertical compliance, which it probably didn’t.
Both systems were presented with the knowledge only one would be taken to market. In another era, the apparent UK/US divide might have foretold a contentious battle. Instead, a post-war spirit of unity seemed to prevail, as we see the Brits acting decidedly Canadian in their polite deference to the superior tech:
The Westrex system, developed in the U. S. with the knowledge and encouragement of the major record companies, seems to have the edge on the London system as to the possibility of final acceptance, and London spokemen said they were not touting their system to the exclution of the other but that they would go along with whatever U. S. record companies wanted… ⁽³⁾
Practical concerns, in the end, made 45/45 the obvious choice. Consider the playback of lateral (mono) records using a stereo pickup. A lateral-vertical pickup could physically handle a mono disc, but playback would send the mono signal to only one speaker, leaving the other sitting silent. By contrast, a 45/45 pickup would more naturally send the mono signal to both speakers at once.
Vertical-lateral also fell short on the question of noise and rumble. The vertical plane holds a much higher potential for rumble in particular, so choosing one channel to bear the entirety of its shortcomings meant that channel would sound noticeably worse than the other (see the StereoDisk white paper⁽⁴⁾). The 45/45 system eliminated that physical imbalance, giving both channels equal share in the horizontal and vertical planes.
Methodology essentially put to bed, the question turned to equipment. Westrex looked for early industry adopters to foster development of a stereo cutting head, their prototype “3A.”
Les Koenig bought one.
The Westrex 3A “StereoDisk” Recorder
Koenig & Co. laid down its first stereo recordings in July 1956. Ten months later, they released their first stereo deliveries: a half-dozen titles on 7.5-inch two-track reel-to-reel tape on the Contemporary Tape sublabel (see From Mono to Stereo Records).
As they concurrently assembled the in-house lathe, it’s clear that future-proofing for stereo was the priority.
illustration of the 3A bits and bobs
3A underside
So they jumped at the chance to be on the stereo front lines with the Westrex 3A, but being first adopters meant working out any kinks… and kinks there immediately were. The 3A was built to be paired with Westrex RA-1574B cutting amplifier, which the 8481 engineers quickly dispensed with. Per Thomas Conrad’s Stereophile piece⁽⁵⁾ (bolding mine):
Their first stereo masters cut with the Westrex head "sounded terrible," and technical assistance from Westrex was not helpful. So Howard and Roy built their own 100W tube amplifier.
"Those tubes would get red-hot," Roy remembers. "Fiddling around with condensers and resistors and coils and whatnot, we were able to EQ this terrible-sounding signal so that the finished track sounded almost like the original."
With the 3A and its propriety cutting amp, Contemporary/GTJ had its stereo cutting system ready to go. At this stage, though (early 1958), the market was theoretical and Koenig was hesitant to release stereo discs into a world unable to play them.
… the company “will issue stereo disks as soon as there are enough play-back cartridges on the market.”
— The Billboard, March 31, 1958⁽⁶⁾
So, the chicken-and-egg problem: too few stereo titles and too few stereo pickups.
The stalemate didn’t last long. By the summer, stereo vinyl had arrived.
Stereo Records
Stereo Records collected stereo titles from Les Koenig’s labels under a single imprint. (For more about the sublabel, see From Mono to Stereo Records.)
Several of these jackets front-loaded STEREO as equal to the artist and title; a marketing move to be sure, but also a warning. Non-compliant lateral cartridges (ie. mono cartridges without physical vertical compliance) could wreck both the record and cartridge by attempting to play true stereo LPs, so shouting STEREO told mono-only customers to stay far away.
Each SR title also had a compulsory warning stripe above the liner notes. These name-dropped the 45-45 “StereoDisk” system, as did the classic technical data box, which more specifically referenced the 3A head.
The vast majority of Stereo Records titles mention the 3A. However specific head model disappears after S7024, coinciding (?) with introduction of the 3C head.
Mono, 1958:
a Grampian head?
The printed technical data on MONO records during this early stereo period starts to reflect multiple cutting head brands. Westrex is initially named, but in 1958 this changes to Grampian, referring to the British audio firm and (most likely) its mono B1/AGU cutting head. This was a reputable beast and Rudy Van Gelder’s cutting weapon of choice on the other coast.⁽⁷⁾
are you my cutting head?
Let’s look at the data to understand what happened here. Below are titles C3537 through C3561 alongside the cutting head listed in the original jacket’s technical data and the lead-out groove style of the first mono pressing. As I think I said in Vol. 1, printed jacket data should be interpreted more generally applicable to the label than specific to the actual title. Lead-out grooves speak to the actual cutting location (Capitol or Contemporary) whereas printed cutting head info will speak to Contemporary’s equipment close to the time of release for that title.
So what do we see above? We see Contemporary slot in a Grampian head for mono mastering during the Stereo Records era when stereo cuts were made with the Westrex 3A. Or at least that’s what the jackets imply.
We can only hypothesize why exactly the Grampian was brought in. The stereo 3A was technically capable of cutting a lateral mono groove⁽⁴⁾, but this data might point to a conscious decision to not use it for that purpose. Perhaps they tried the 3A for mono (thus the Westrex printed on mono C3537, 38, 40, and 42) but the cuts started showing flaws, or simply couldn’t match level with the Westrex mono heads Les K had enjoyed at Capitol.
The tech data changes back to Westrex in early 1959, timing which dovetails nicely with the introduction of the second-gen Westrex 3C stereo head⁽⁸⁾ (more on that in a second). Maybe the new 3C solved whatever the 3A’s mono problems were and gave Contemporary/GTJ an two-in-one cutterhead that never had to be swapped out.
Obviously, there is a lot of guesswork happening here…
… and here’s more:
The guys at 8481 were concerned with cutting amp power, right? So we can imagine Grampian might mean the high-powered mono Grampian-Gotham cutting system, an advertised pairing most notably used by Rudy Van Gelder through this period to cut some of the loudest slabs in the history of jazz.
For more information on the development of that system, check out Richard Capeless’s excellent site RVG Legacy. As he explains: Rudy acquired the Grampian head but found its companion amplifier lacking in power, so he turned to Gotham Audio to build him one better, and thus the Grampian-Gotham system was born.⁽⁷⁾
By 1958, this marketed combo was a few years old and could quickly deliver a readymade solution for mono cutting. So… is that what happened at 8481?
I don’t know. Re the Gotham half of the system, assuming without evidence that it was part of the 8481 system isn’t great science. Perhaps if we better understood the prominence or widespreadedness of the G-G combo at that moment in time, we could more faithfully make the leap. Were any American engineers worth their salt using the Grampian head without the Gotham amp? That would be helpful information.
Plenty else remains unclear, most notably what titles were actually cut with this head or that head. Did some mono titles feature the Westrex 3A head in mono configuration? Did a Westrex 2B head enter the fray at any point? The possibilities are numerous!
Given the limited data we DO have, my present hypothesis is that most of the early mono lacquers at 8481 were cut with the Grampian mono head.
The Westrex 3C
The final six Stereo Records titles eschewed the “3A” from their jacket technical data, possibly due to Westrex introducing a successor. To stay on the cutting edge, Contemporary traded in the original 3A for the new 3C.
This was a big step forward. Over the previous year of testing and development, Westrex had identified resonant peaks in the 3A frequency response which were in turn causing significant crosstalk between left and right channels. Making incremental design changes to an experimental model of the StereoDisk head, they identified the stylus support tube as the “main deficiency of the [3A] design.” By then stiffening the support and building a new mounting to prevent torsional stylus movement, they were able to smooth out the frequency response and make significant reductions in crosstalk (3C white paper).⁽⁸⁾
Contemporary would cut with this single head for the next five years. I consider the Westrex 3C the paintbrush of peak Contemporary; it’s with the 3C that DuNann & Holzer developed the lasting Contemporary school of mastering. The 3C cut the lacquers which cemented the Contemporary legacy in vinyl history.
Despite my admiration for this period, data is short— so we’re about to start moving much faster through time. Let’s fast forward to 1962 to see the full accounting of Contemporary’s mastering situation in this general 1959-64 period:
Liner notes, S9006 Sounds Unheard Of!
1962 Inner Sleeve.
Both of these mention the 200-watt HAECO amp… HAECO was Howard Holzer’s new company name (Holzer Audio Engineering Company), but these were the same amplifiers Holzer and DuNann put together in 1957. No doubt modifications and improvements were made over the years. The amps were finally retired around 1978.
The Mastering Console
The Westrex 3C was a significant step forward for Contemporary’s sonic ambitions. The 3A could be wrestled using capacitors or whatever to shape the sound into something acceptable; still, its technical shortcomings meant limited creative freedom. The more competent 3C blew open the door to finer mastering control.
The Contemporary mastering console exercised that control. DuNann and Holzer had put together a rack of specific equipment suited for jazz recordings and their specific flat style of capture. It had been built earlier in 1957/8, but it wasn’t until the 3C arrived that the minute control offered by the console was finally uncuffed — and you can fully hear that flexibility in Contemporary’s early 60s work.
I’d be really chuffed to find any old image of the thing. Even the most off-axis, out of focus shot would give us a better frame of reference than words. Until we find some evidence, imagine the Contemporary mastering console thus: a vertical rack with multiple beefy components secured in place, with a handful of knobs on each. The knobs are the power: with them, the engineers could fine-tune and manipulate sound on the fly.
John Koenig recalled that the Contemporary system was built so the master tape “would be taken and actually played back on one of the machines that recorded them,” after which “it went to our mastering rack [the console] to our lathe.”⁽⁹⁾ Details of the console have been discussed in more detail by Bernie Grundman, who worked the Contemporary lathe from 1966 to 1968 (a little more on him soon). Per his description⁽¹⁰⁾, the console offered:
Level control and two bands of “generalized” EQ “available at any one time” for each channel.
Frequency-specific panning for each channel. An example: it “had special panning systems for the frequency bands where you could actually pan the cymbal to the center, just the high frequencies…”
Send and return reverb, by which the engineers would continuously adjust injection of EMT plate reverb (Contemporary had a mono EMT plate) into the music. Bernie recalled Les Koenig’s instructions thus: “he didn’t want to draw any attention to it. It was like we would bring it up until we could hear it and then we would take it back… so it was something more you just felt but you couldn’t identify it… it just made it open a little bit.” More notes on reverb can be found in Mastering History Vol. 4.
These features probably don’t sound special to us denizens of the future, but in the late 1950s these were not common pieces of mastering systems. It’s not that other labels weren’t futzing with sound; it’s that few left it for the cutting stage.
Lester and the boys, thoughm packed these features into mastering as a way of preserving fidelity. They certainly could have applied adjustments between two tape machines and made EQ’d copies from which to cut lacquers. Perhaps they even experimented with it. Such a process would have created ready-to-go tapes for efficient recuts down the road. Still, mastering directly from the first-generation masters was cleaner and sonically superior, even if more inconvenient. Les was uncompromising when it came to sound.
So lacquer cuts — even the third or fifth or nth cuts made decades after the originals — could turn into whole day affairs. Manning the console took intricate planning and the engineers would choreograph adjustments down to the granularity of specific solos and passages. Bernie:
Lester and I would sometimes take a day or two to cut one album… you had to have it all mapped out. We do ‘this’ on this song. We do ‘this’ at the sax solo, etcetera, etcetera. So, we would have all of these things written out and we would have to adjust it. As an example, on the right side, if the trumpet comes in and it’s not quite loud enough, and the bass is there too, well, you have an equalization there and you have a level control. So, on the right channel, as soon as that trumpet comes in, you roll off the bass, but turn up the level. So now the bass stays where it is, but the trumpet comes up.⁽¹¹⁾
This is really cool! It’s also why Koenig-era Contemporary cuts are an entirely different creature than most analog and digital masterings that have come since. Critical to the Contemporary mastering approach was a mandate for the cutting engineer(s) to editorialize while creating a proper musical and sonic presentation.
Mono Mastering, 1959+
Two-track 50/50 master tapes…
Hey I’ve done a whole deep dive about this! There I’ve broken down tape number data and theorized a 50/50 line in late 1958, after which Contemporary stopped recording to full-track (mono) and captured sessions in two-track (stereo) only.
A single master tape meant more streamlined editing and mastering. By way of precise microphone and mixer technique, the engineers were able to ensure that new stereo recordings could be used “50/50” to cut mono lacquers. 50% right and 50% left is the idea; the channels were to be summed during mastering into a mono signal.
The technique was likely more multistep than it sounds, of course, involving custom mixing and EQing of the channels prior to summation. Though it would be nice to hear the perspectives of engineers to better understand the process.
Mono cuts with a stereo head…
There was a similar consolidation towards stereo tech in cutting technology. Contemporary might have turned to the Grampian mono head in 1957 or 1958 while using the 3A for stereo, but with the arrival of the 3C in 1959, they definitively began using the stereo head to cut mono lacquers.
So let’s talk about how exactly a stereo head cuts a mono LP.
The question hinges on polarity. Put simply, a sound wave travels through positive and negative voltages. Inverting a sound wave’s polarity flips the sound wave so the positive becomes negative and vice versa.
Two identical signals with inverted polarity. Source: Mackie
Graphic from Audio University shows inverted polarity achieved by reversing the wiring on the bottom signal.
Now let’s consider this with regards to the physics of the groove. The 45/45 head has coils that “push” and “pull” corresponding to the polarity of the sound wave in that channel.
Assuming identical signals are sent to these two coils:
If those coils are wired with THE SAME POLARITY, they will both “push” or both “pull” at the same time. This results in a VERTICAL groove with no lateral movement.
If the coils are wired with OPPOSITE POLARITY, one will “push” while the other “pulls” and vice versa. This results in a LATERAL groove with no vertical movement.
A top priority when developing the 45/45 system was maintaining backwards compatibility with lateral mono discs. To accomplish this with stereo cartridges, their coils are wired with opposite polarity.
This inversion has to also be accounted for in the cutting stage. Thus, the stereo 45/45 cutting head also has coils wired with opposite polarity.
In summary: the cutting head inverts the polarity of one channel, and the pickup cartridge inverts it back.
So how exactly does the engineer cut a mono record using the stereo 45/45 head?
It’s not complicated. They simply send identical signals to both channels of a stereo 45/45 head. Because the coils are of opposite polarity, the result will be a lateral mono cut.
Because of inverse polarity, a mono signal sent to both coils cuts a lateral groove (animation credit VinylRecorder)
the end of “true” mono?
If that felt like a lot of rigamarole to get to such a simple explanation, understand there remains an obsessive pocket of audiophilia which fixates on true mono cutterheads and remains unsatisfied with stereo heads attempting mono cuts.
It’s difficult to endorse their suspicions about stereo heads cutting mono, though in the same breath it’s difficult to argue against the guarantees a true mono head provides. Ultimately the execution comes down to the engineer, and they as a species have been far fom infallible. Many 1960s-onward mono records have been cut incorrectly, and no I don’t mean the intentional fake stereo efforts of the 60s and 70s — I mean engineers have made mistakes like introducing timing errors when reading a mono tape with a two-track head or passing parallel mono signals through mis-calibrated stereo equipment.
Amidst these errors and oversights, it’s easy to miss the fact that 45/45 stereo heads have always been mechanically capable of cutting purely lateral grooves. Any competent cutting engineer can make a “true” mono cut with a stereo head (though the question of stylus size is mired in additional superstition).
Mastering engineer Kevin Gray recently addressed this and the cutterhead polarity issue (via email to a Steve Hoffman Forums user; bolding mine), noting that “the idea that cutting mono with a stereo cutterhead is somehow ‘less mono’ is a fallacy. I would guess that by 1965 all mono cuts were done with stereo heads.” ⁽¹²⁾
Contemporary was ahead of that timeline; they stopped using a mono head after 1958. The Grampian evidence suggests the Westrex 3A might have not been used for mono cuts (for whatever reason), but changes to jacket language in early 1959 show that the 3C actually was.
The 3C’s introduction also coincided with Contemporary’s repositioning of stereo releases under the regular masthead (and the retirement of Stereo Records). Like the hybrid “banner” design scheme made to govern mono and stereo variants, a single cutterhead would now cut both mono and stereo lacquers.
I’m guessing they sold off the Grampian.
We’re not going to find much written historical evidence when it comes to mono-with-a-stereo-head question, but some subtle language in the GTJ & CR News (June 1959) speaks to the stereo/mono hybridity in both recording (thus, 50/50 master tapes) and mastering (thus, stereo head for mono cuts).
Lester at the lathe
We’re about to dip into a foggier period: the mid-1960s.
Howard Holzer was Chief Engineer at Contemporary through the early 1960s. Roy DuNann was still there; and per the Sounds Unheard Of! liner notes (mid-1962), his title was Vice President in Charge Of Recording.
The last Contemporary/GTJ session to credit Roy* is 12047 Enjoy The Good Old Days With The Banjo Kings, recorded May 21, 1962. Soon after this, Roy departed Contemporary and Los Angeles and settled in Phoenix, Arizona. Per Thomas Conrad’s profile, “his first wife's asthma was an important factor in the move.”⁽⁵⁾
*he would later receive credit on some mid-1970s Contemporary stuff, once he was working at A&M.
Howard Holzer stuck around 8481 for a few years post-Roy, and thus gets sound credit on every recording through 1964.
Simultaneously, though, he was building equipment venture HAECO (Holzer Audio Engineering Co.). The earnest beginning was Contemporary’s 1958 power amp (HAECO Serial No. 1), but his tinkering had since consolidated into a separate business with clients industry-wide. Given Contemporary’s tapering musical output, 8481 Melrose was no longer the place to be for a man on the cutting edge.
Holzer finally made his exit in late 1964 or 1965.
HH making moves in Billboard, 2/27/1965
3616 Here and Now, the only title recorded in 1965, cements Holzer's exit with sound credit given to Les Koenig and Mark Taylor.
So what was to come of Contemporary’s mastering operation with its two creators departing the firm? Few new titles were coming forth from Contemporary/GTJ in this period but the catalog remained in-print and new lacquers would often be needed to keep up with demand. And somebody needed to cut them.
The answer is simple— Lester Koenig had the facility’s development from the beginning, and so long as he remained, the work continued. He didn’t simply own the lathe; he’d cut with it and operated it side-by-side with his engineers. With those engineers now gone, he continued cutting lacquers as the label’s primary cutting engineer.
It’s often wrongly asserted that LKS or LKL in the runouts denotes cutting by Lester Koenig (these were just the prefixes for tape numbers), but in spirit that idea is not far from the truth. Lester was the arbiter of Contemporary’s sound from the beginning, whether his hands met controls or not.
The Westrex 3D
In 1964 Westrex introduced the next iteration of its StereoDisk cutting head, the 3D. Given five years since dropping the 3C, they’d busily amended several elements of the design (see the Westrex 3D white paper from July ‘64).⁽¹³⁾
3D improvements.
There were certainly other brands making stereo heads through this period, but Westrex remained the industry standard by continuously iterating on excellence. Per Radio-Electronics Magazine, the StereoDisk refresh delivered “increased dynamic range and smoother frequency response, especially in the high-frequency range.”⁽¹⁴⁾
Contemporary stuck with Westrex and replaced its 3C with the 3D. (Around this time Rudy Van Gelder transitioned from a Fairchild stereo head to a Westrex⁽⁷⁾).
Radio-Electronics Magazine, October 1964
The 3D would be final letter in the StereoDisk alphabet, though several further iterations would be introduced over the next decade, including the 3DII (c. 1970?), 3DIIA, and its helium-cooled variant 3DIIAH. I’d love to learn more about these and whether Contemporary had them or not or when. We might get more clarity in the future.
The story continues in Vol. 3 >
Sources
Boden, Larry. Basic Disc Mastering. 1978. 3rd ed., 2022.
Cable, Gene. “Scanning around with Gene: Listening to Music with Both Ears.” CreativePro, 12 May 2006, creativepro.com/scanning-around-with-gene-listening-to-music-with-both-ears/. Accessed 2023.
Jazz Discography Project. “Contemporary Records Discography Project.” Jazz Discography Project, www.jazzdisco.org/contemporary-records/. Accessed 2020.
(1) Henning, Harley A. Sound Reproducing System. no. 2025388, 24 Dec. 1935, patents.google.com/patent/US2025388A/en?oq=2025388. Accessed 2023.
(2) Blumlein, Alan Dower. Improvements in and Relating to Sound-Transmission, Sound-Recording and Sound-Reproducing Systems. no. GB394325A, 14 June 1933, patents.google.com/patent/GB394325A/en. Accessed 2023.
(3) “Editor’s Review.” Audio, vol. 41, no. 11, Nov. 1957, p. 16. World Radio History.
(4) Davis, C. C., and J. G. Frayne. “The Westrex Stereo Disk System.” Proceedings of the IRE, vol. 46, no. 10, Oct. 1958, pp. 1686–93, https://doi.org/10.1109/jrproc.1958.286745. World Radio History.
(5) Conrad, Thomas. “The Search for Roy DuNann.” Stereophile.com, Apr. 2002, www.stereophile.com/interviews/402roy/index.html. Accessed 2020.
(6) “Contemporary Signs Hentoff to A&R Pact.” The Billboard, 31 Mar. 1958, p. 5.
(7) Capeless, Richard. “Mastering Equipment.” RVG Legacy, 2020, rvglegacy.org/mastering-equipment/. Accessed 2022.
(8) Frayne, John G., and R. R. Davis. “Recent Developments in Stereo Disc Recording.” Journal of the Audio Engineering Society, vol. 7, no. 4, Audio Engineering Society, Oct. 1959, pp. 147–52, 180. Accessed 2023.
(9) Acoustic Sounds. “An Interview with John Koenig, Former President of Contemporary Records.” YouTube, YouTube Video, 22 Apr. 2022, www.youtube.com/watch?v=GAsuVLN_lyo. Accessed 2022.
(10) Acoustic Sounds. “Contemporary Records Mastering Session with Bernie Grundman, Chad Kassem, and John Koenig.” YouTube, YouTube Video, 13 May 2022, www.youtube.com/watch?v=LgbPnzDmYEU. Accessed 2022.
(11) Grundman, Bernie. “A Talk with Vinyl Mastering Engineer Bernie Grundman – the Secrets Interview.” Secrets of Home Theater and High Fidelity, interview by Carlo Lo Raso, 29 Sept. 2022, hometheaterhifi.com/features/factory-tours-interviews/a-talk-with-bernie-grundman-the-secrets-interview/. Accessed 2023.
(12) Gray, Kevin. Email response per user Jasonbraswell on “'Tone Poet' Jazz Reissue Series.” Steve Hoffman Music Forums, 23 Dec. 2022, https://forums.stevehoffman.tv/threads/tone-poet-jazz-reissue-series.795822/page-1606#post-31085893.
(13) Nelson, C. S., and J. W. Stafford. “The Westrex 3D StereoDisk System.” An Anthology of Articles on Disk Recording from the Pages of the Journal of the Audio Engineering Society Vol. 1-Vol. 28 (1953-1980), Audio Engineering Society, 1980, pp. 260–67.
(14) Augspurger, G. L. “New, Higher-Fi Stereo Disc Cutter.” Radio-Electronics, vol. 35, no. 10, Oct. 1964, p. 49. World Radio History.