Skip to content
RESONON

Draw an Automation Curve

automation() is a curve through breakpoints, placed in cycles; signal_ramp() is a straight line. Both are in std/signals, and either can drive anything you set with <<. Signals & Time explains how a signal keeps time.

Place the breakpoints

Section titled “Place the breakpoints”

Give automation() #[time, value] breakpoints, with the time in cycles:

use "std/instruments" { Sampler, Kit };
use "std/effects" { Lowpass };
use "std/signals" { automation, signal_ramp };


let drums = AudioTrack("drums");
drums.set_instrument(Sampler(Kit("CR-78")));
drums << [bd sd bd sd];


let filter = Lowpass("lowpass", 800);
drums.set_effects(#[filter]);


let sweep = automation(#[0, 0.0], #[2, 1.0], #[4, 0.3], #[6, 0.0]);
filter.parameter("Cutoff") << sweep.range_exp(200, 4000);


PLAY;

The first value holds before the first breakpoint, and the last after the last one. Breakpoint times are counted in the signal’s timebase: for times in seconds, add .set_timebase(seconds(1)); for beats, .set_timebase(beats(1)).

Shape each segment

Section titled “Shape each segment”

A third element sets the curve of the segment that starts at that breakpoint:

let shaped = automation(
    #[0, 0.0, "smooth"],
    #[2, 1.0, "ease-out"],
    #[4, 0.3, "step"],
    #[6, 0.0]
);
filter.parameter("Cutoff") << shaped.range_exp(200, 4000);

The curve names are listed under automation.

Draw a straight ramp

Section titled “Draw a straight ramp”

signal_ramp(start, end) rises in a line over one cycle and repeats; a third argument stretches it over several cycles:

filter.parameter("Cutoff") << signal_ramp(0, 1, 4).range_exp(200, 4000);

Running the line again restarts the ramp at the next cycle boundary.

Section titled “Related”