[sdiy] suboctaves

[Dave Krooshof]

>> how do I accomplish /1.5?
>
>With 50% duty cycle it is tricky. You multiply by 2, then divide by three.
>Multiplying by 2 is the hard part... you can full wave rectify a triangle if
>you have one available, or use several comparators and a sawtooth to get
>multiple pulses from a single cycle input.

Makes me think about a synth keyboard with one steady oscillator,
tuned to the centre frequency of your harmony.
Then all notes are derived from that single tone by multiplying
and deviding. This way you can get the (ancient) Just Intonation!!

And with just a few keys controlling dividers and multiplyers
you can obtain a wide frequency range. You'll have to learn
a new fingering, but hey, that's easy for a musician.

You could use only 2 and 3 to multiply and devide, to obtain
a set of frequencies that are close to all 11 notes found in an octave.
they differ from what a pianist is used too, yet it will sound very
precise to you. This system is described by our all time famous Greek
hero Pythagoras. (Yes, the triangle guy did more for us).

Allowing a 5 in the system (next prime) gives a different set
of notes, which sound very bluesy. This is why blues guitarists
playing in E tend to bend the G note up.

A resitor bank deviding by 2root12 will give you tempered intonation
which is like a communist approach: All notes are equal.
The system was - however- a democratic choice made in London in the
1940's. They decided 440 was the central A. Bogus.
It is only interesting when you mudulate a lot, meaning changing
the centre frequency, here. Bach sounds better in tempered intonation.*



Dave Krooshof



*Wim de Bie played Bach on his Mouth sythesizer. Very high tech:
Small enough to fit in his mouth, yet containing thousands of fuses!