Buffer-based Parameters

This tutorial shows how to use buffers to control audio parameters. In this case, we use a buffer to control the frequency of an oscillator to achieve classic FM synthesis.

buffer-based_parameters.bell

## buffer duration
$dur = 3000;
## carrier frequency
$carfq = 220;
## harmonicity ratio
$harmratio = 1.333;
## modulation index as a equidistant linear envelope
$modindex = 0 5 0;
## modulator frequency
$modfq = $carfq * $harmratio;
## generate modulator oscillator buffer
$mod = cycle(
    @frequency $modfq @duration $dur
);
## apply audio processing to modulator buffer
$mod = $mod.process(
    ## multiply amplitude
    multiply($modfq * $modindex) 
    ## apply offset to oscillate around carrier frequency
    plus($carfq) 
);
## generate carrier oscillator buffer
$car = cycle(
    ## use modulator buffer as frequency
    @frequency $mod
    ## we need to ensure carrier and modulator buffers match in duration
    @duration $dur
);
## we only transcribe carrier buffer and render it
$car.transcribe(@gain .125);
render(@play 1)