[LAU] A bit of a puzzle

Will Godfrey willgodfrey at musically.me.uk
Fri Apr 30 17:00:34 CEST 2021

On Fri, 30 Apr 2021 16:46:22 +0200
Fons Adriaensen <fons at linuxaudio.org> wrote:

>On Fri, Apr 30, 2021 at 03:06:28PM +0100, Will Godfrey wrote:
>> As it happens, I've had answers from elsewhere. It seems people are using it
>> for experimental sounds, and also when they want enharmonic, but key/pitch
>> related sounds for things like percussive instruments.  
>But what exactly does it do ? 

At zero all notes sound 440Hz. As you wind it up they start to spread apart
either side of MIDI A4, at the half way point The scale becomes the same as
normal equal temperament. Beyond that the law changes and the pitch spread is
dramatically greater.

The actual code (in the SubSynth engine) is:

notefreq = 440.0f;
int fixedfreqET = pars->PfixedfreqET;
if (fixedfreqET)
{   // if the frequency varies according the keyboard note
    float tmp = (midinote - 69.0f) / 12.0f * powf(2.0f, (((fixedfreqET - 1) / 63.0f) - 1.0f));
    if (fixedfreqET <= 64)
        notefreq *= powf(2.0f, tmp);
        notefreq *= powf(3.0f, tmp);

Will J Godfrey
Say you have a poem and I have a tune.
Exchange them and we can both have a poem, a tune, and a song.

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