Imitation is the highest form of flattery

We attended a concert last week at the Danish Guitar Camp, where Carlo Marchione played a collection of music written for various instruments in the 1700s. One of those pieces was an arrangement of the Adagio from Mozart’s Klaviersonate in B-Major K. 570, which I had never heard before.

As soon as he started, I thought…. waitaminute…. this tune sounds awfully familiar… as a Canadian…

wait… what?

Have a listen to the first 10 seconds of the Mozart, then listen to the first 10 seconds of the Canadian National Anthem. I suspect that Calixa Lavallée might have had the Mozart tune in the back of his head when he sat down to work on Théodore Robitaille’s commission.

Dynamic Styli Correlator Pt. 1

Many audio recording systems are based on a concept known as “pre-emphasis” and “de-emphasis”. This is a process where a signal is distorted (here, I use the word “distorted” to mean “changed”, not “clipped”) at the recording or encoding process to counter-act the effects of something that will happen at playback. One example of this is a RIAA equalisation that applies an overall bass-heavy tilt to the frequency response at playback, and therefore the signal is given the opposite tilt when it’s cut onto the vinyl master. Dolby noise reduction for analogue magnetic tape follows a similar philosophy.

Another type of intentional distortion applied to an audio signal is based on assumptions of what happens at playback. Mixing engineers for television often emphasise lower frequency bands, assuming that everyone’s television loudspeakers needed some help. Pop and rock recording engineers check the mix on a low-quality mono loudspeaker and may make adjustments to the mix – to make sure it survived a clock radio or a portable Bluetooth loudspeaker (depending on which decade we’re talking about). Stereo vinyl records can’t have big low-frequency differences in the two audio channels otherwise the needle will hop out of the groove, so they’re mixed and mastered accordingly.

I’ve been reading “The RCA Victor Dynagroove System”, by Harry F. Olsen, published in the April 1964 issue of the Journal of the Audio Engineering Society. In it, he describes the entire recoding chain, including something that piqued my interest called a “Dynamic Styli Correlator” which is a distortion that is applied to the audio at almost the last stage of the signal path before it reaches the cutter head of the lathe that creates the lacquer master. You can see it here in Figure 1 from the article (I drew the red box around it).

Cool name; almost worthy of Dr. Heinz Doofenshmirtz (although it’s missing the “-inator”). But what is it?

One of the problems with playing back a vinyl record is that the shape of the needle on your turntable is not the same shape as the cutting stylus on the lathe. Consequently, the path that the needle tracks is not exactly the same as the path of the stylus. The result of this mis-match is that the electrical input signal that is used to make the master (the original recording) is not the same as the electrical output signal that comes out of your turntable (what you hear).

The idea behind the Dynamic Styli Correlator was that the actual path of the playback needle could be predicted, and the groove cut by the stylus could be modified to ensure that the output was correct. In other words, the distortion caused by the playback needle was estimated, and a distorted groove was cut to make the needle behave. This is shown graphically in Figure 29 of the article:

This is a great idea if the system works and if the prediction of the playback needle’s path is correctly predicted. However, neither of these two assumptions is guaranteed; so a number of things can go wrong here, and if anything can go wrong, it probably will.

However, it does mean at least as a start, that if you play an old RCA Victor Dynagroove record with a stylus shape that wasn’t invented yet in 1964 (say, a contact line stylus made for CD-4 Quadraphonic records, for example). Then you might wind up doing a much better job of reproducing the distortion that RCA created in the first place, instead of what they thought you were supposed to hear.

Wow

This article, from The Gramophone magazine, August 1932 foretells the future of turntables with platters driven by electric motors. Note that, to test this particular one, they increased what we would today call the “tracking force” to 3.5 pounds (about 1.6 kg) on the outside groove of a 10″ record without reducing the speed. Try that on a turntable today…

Sad to see a familiar mantra here though: “the motor is remarkably efficient, very well made and ridiculously expensive.”

Historical Context

This episode of 99 Percent Invisible tells the story of the Recording Ban of 1942, the impact on the rise of modern jazz music, and the parallels with the debates between artists and today’s streaming services. It’s worth the 50 minutes and 58 seconds it takes to listen to this!

At the end of that episode, the ban on record manufacture is mentioned, almost as an epilogue. This page from the January, 1949 issue of RCA’s “Radio Age” magazine discusses the end of that ban.

Interestingly, that same issue of the magazine has an article that introduces a new recording format: 7-inch records operating at 45 revolutions per minute! The article claims that the new format is “distortion free” and “noise-free”, stating that this “new record and record player climax more than 10 years of research and refinement in this field by RCA.”

Fibre needles

Reading through some old magazines again…

This time, it’s The Gramophone magazine from October, 1930. In the editorial, Compton Mackenzie says

What caught my eye was the discussion of gramophone needles made of “hard wood”, and also the prediction that “the growth of electrical recording steps … to grapple with that problem of wear and tear.”

The fact that electrical (instead of mechanical) recording and playback was seen as a solution to “wear and tear” reminded me of my first textbook in Sound Recording where “Digital Audio” was introduced only within the chapter on Noise Reduction.

Later in that same issue, there is a little explanation of the “Electrocolor” and “Burmese” needles.

The March 1935 issue raises the point of wear vs. fidelity in the Editorial (which starts by comparing players with over-sized horns).

I like the comment about having to be in the “right mood” for Ravel. Some things never change.

What’s funny is that, now that I’ve seen this, I can’t NOT see it. There are advertisements for fibre, thorn, and wood needles all over the place in 1930s audio magazines.

The Phono Gram

Late-night free-floating anxiety is not a modern phenomenon. One of my favourite descriptions of it is Dorothy Parker’s 1933 short story called “The Little Hours”, published in The New Yorker.

However, more than 30 years before this, The Phono Gram magazine published the following, which a Dr. J. Leonard Corning proposed to cure the problem of late-night melancholy with what we would, today, called a “pair of headphones” (although the design that he describes probably wouldn’t sell well to anyone who is not interested in S&M…) playing Wagnerian arpeggios and minor chords. (Personally, I just put the timer on my iPhone to turn off after 30 minutes, and turn on an old episode of “QI” or “8 Out of 10 Cats Does Countdown” – Sean Lock’s voice drowns out my own internal ones.)

I’ve removed a rather significant portion here…

Loud speaker

I live in Denmark where people speak Danish. One interesting word that I use every day is “højtaler” which is the Danish word for “loudspeaker”. I say that this word is “interesting” because, just like “loudspeaker” it is actually two words glued together. “Høj” means “high” or “loud” and “taler” means “talker” or “speaker” (as in “the person who is doing the talking”).

Sometimes, when I have a couple of minutes to spare, instead of looking at cat videos on YouTube, I sift through old audio and electronics magazines for fun. One really good source for these is the collection at worldradiohistory.com. (archive.org is also good!). Today I stumbled across the December, 1921 edition of Practical Electrics Magazine (which changed its name to The Experimenter in November of 1924 and then to Amazing Stories in April 1926*) It had a short description of a stage trick called the “Haunted Violin”, an excerpt from which is shown below.

The trick was that a violin, held by a woman walking around the aisle of the theatre would appear to play itself. In fact, as you can see above, there was an incognito violinist with a “detectophone” that was transmitting through wires connected to metal plates under the carpet in the theatre. The woman was wearing shoes with heels pointy enough to pierce the carpet and make contact with the plates. The heels were then connected with wires running through her dress to a “loud talker” hidden inside the violin.

Seems that, in 1921, it would have been easier to learn at least one word in Danish…

Side note: This is why, when I’m writing about audio systems I try as hard as possible to always use the word “loudspeaker” instead of “speaker”. To me, a “speaker” is a person giving a speech. A “loudspeaker” is a thing I complain about every day at work.

* That April 1926 edition of Amazing Stories had short stories by Jules Verne, H.G. Wells, and Edgar Allan Poe!

Post Script:
My wife reminded me that it’s the same in French: “haut-parleur”. It’s a reminder that the original loudspeakers were never intended for music, I suppose…