When singers sing, or players of string or wind instruments sound a note, they almost always apply some vibrato — that familar effect in which the pitch is varied slightly, and rapidly — if the note is to be held for long. It is particularly unusual (in modern times at least) to hear singers who don’t do this, and when they don’t it has a tense, unsettling effect. I was just listening to some Chet Baker an hour or so ago, and it dawned on me that part of the haunting quality of his singing was that he used very little vibrato. (Even he didn’t avoid it altogether, though.)
Throughout much of my recording career we recorded on magnetic tape. I won’t go too far into the technical details, but recording on magnetic media involves forcing magnetic particles, embedded in a physical matrix, into particular alignments, using a varying magnetic field applied by the recording “head”. When the tape later passes over a playback head, it induces a correspondingly varying field, which is amplified, and passed along to the speakers.
Getting this to happen in a predictable and repeatable way is a formidable technical challenge — it’s tricky to coax the little particles into place in just the right way — and it is particularly difficult to get the system to work evenly with regard to frequency. In other words, if you record a low-frequency tone, say 100 Hertz (100 cycles per second), at a reference level, and a high treble tone, say 10,000 Hz, at the same level, you want them both to play back at the same level. But it’s hard to do this well: in particular, recording the high frequencies accurately is trickier, because the physical size of the pattern on the tape is much smaller, and the little particles have to be shoved around more violently. (There is also a particular problem in making a recording that accurately follows the waveform as it crosses zero at each half-cycle, due to the fact that the field strength applied by the record head is so low at that point that it is too weak to shift the magnetic particles in their matrix.)
But early audio engineers found a sneaky trick: they realized that the particles can be pushed into place more easily if they are “loosened up” a bit as the coercive force is being applied. To do this, a sinewave of irreproducibly high frequency is superimposed on the audio signal. This extra signal is called “bias”, and greatly improves the quality and linearity of the recording.
When I was a little boy, back in the late 1950s and early 1960s, a popular toy was an “electric football” game in which the players lined up little statuettes in formation on a metal board prior to each play. To start the action, you flipped a switch, and the whole board began to vibrate. The little men would skid around almost frictionlessly, and eventually some state of affairs would be reached that meant the down was over.
The point, as far as this post is concerned, is that the vibrating board got everything loose and moving. And anyone who has ever tried to push a heavy appliance across the floor knows that if it gets stuck you give it a shake; as long as you keep it in some sort of motion you can move it quite freely.
All of these things — tape bias, electric football, shaking a fridge to get it moving, and the use of musical vibrato — are, it seems to me, expressions of the same phenomenon, namely that things get stuck if they don’t keep moving. The case of vibrato is the most interesting, I think: it is very difficult for a singer to hold a long note without applying some vibrato (if you can sing, try it yourself), and singing that doesn’t use it has a strange, emotionless, almost suffocating quality. It feels oddly “frozen”.
And that’s the common factor: all of these techniques involve the breaking of some kind of adhesion: not only to a physical matrix, but even to a perceived musical pitch. There is just something about being in motion; it means freedom. Once static friction is overcome, everything is mobile, attentive and ready. It’s easy to see why this would work in the case of tape bias, or electric football games — but that this principle also applies psychologically, in the experience of music, seems to me a very curious fact.