Linear FM input
  • Hello there! I'm new, to the forum, Audulus, and synthesis generally (though I'm a professional musician/music therapist). I decided to learn the synthesis via info on modular synthesis, and have been tumbling down a sonic rabbit hole ever since... And thoroughly enjoying it!

    I have a question about linear FM. In order to produce more musical, and tonally consistent, FM, modules (like the Intellijel Dixie series, of which I'm attempting to build a clone, as a way to learn Audulus building) use a linear FM input. Am I right in thinking to make exponential audio signal linear, one needs to treat it logarithmically? That's as far as I've been able to get - I don't know what expression is required...

    Sorry to bury the lead a touch!
  • Linear FM in Audulus is super straightforward. You add and subtract from the frequency information going into the oscillator.

    There are two modules you will find quite handy. The "Hz2o" module will convert from linear scaling which we think of as Hz (cycles per second) into exponential scaling which we think of as Semitones (one octave means doubling the cycles per second). The "o2Hz" module will do the opposite.

    I made a simple patch to show how I usually go about this in a patch.
    FM Easy Mode.audulus
    Screen Shot 2017-02-22 at 8.24.03 AM.png
    1825 x 778 - 241K
  • Mighty good of you sir, thank you. I'll dig out my iPad and have a look/listen shortly... Should have guessed there was a module for it.