FSK, FM; PLL, ...(was: Re: Overriding MIDI and a (possibly screwy) Idea

[Haible Juergen]

> Uh.... FSK... FSK....  The signal being recorded IS an audio signal!
> No one said a DC signal was being recorded.
>
>
> Personally I think it is possible, but how much tape is needed for one
"word?"

You got the point, exactly.
It is possible to record several signals as FM signals around several
carrier
frequencies, but as with the good old FM broadcast system, each signal
has to be severly band limited in order not to interfere with a
different
band. Every modulation technique has it's own ratio of usable bandwith
vs. used up bandwidth, and SNR of this band - the theory fills books
about communication technique. But in short, generalizing *very much*
(don't beat me for this!) the bandwith of your individual signals would
*add up* until you reach the audio bandwith of, say, 15kHz.
Now don't underestimate the bandwith of CV's. An envelope with
1ms attack time would eat up some 1kHz of these 15kHz alone.
A sine LFO with 100 Hz would take 100Hz only; but if you choose
a square wave with 1ms rise time, you're back in the 1kHz range
again.
As I said, these numbers may just serve as a rule of thump and vary
with the chosen modulation method and and modulation index.
Take it just as a "poor man's Heissenberg Relation" (;->)

JH.