M4L Pitch2Level

This device is made to work with the Ableton Looper Effect. It modifies the Y track volume’s level depending of the looper’s pitch/speed X value : Y = F(X). Pitching/speeding makes an offset in the spectral content, resulting in more or less presence for high and/or low frequencies. Track’s volume is also auto-adjusted to reduce/add presence.

Device location

Put the device anywhere on the track where you use the Looper effect (it should be detected).

Set Levels (db)

Use the colored sliders to set levels (from -18 to +6db) for each integer pitch values (-36 -24 -12 =0 +12 +24 +36).

Interpolation

Once levels are set, a curve DB LEVEL = F(PITCH) is calculated. It will interpolate level adjustement (especially useful for continuous pitch variations when using pitch knob instead of arrows). The interpolation returns Yi_db. To convert this db value to a linear value to control the mixer we modelize the response with a polynomial :  Yi_linear is calculated with a polynomial P. In order to improve CPU usage we chose a 2nd-degree polynomial. To summarize : 1— we define F behaviour with settings 2— F interpolation returns a db value in function of pitch 3— this value is converted into linear value that controls the mixer object. Due to errors the resulting Yi_db is ±0.5 db compared to the expected value.

FIX 0 button

Click to quick re-ajust the mixer level to the db value chosen for the =0 pitch.

Functions

Xn = Pitch [-36 +36]

Yn = Level [-18 +6] db

(Xn,Yn) → F

X = continuous Pitch [-36. +36.]

Yi_db = F(X)

Yi_linear = P(Yi_db)

Yi_linear → Mixer object