Aratu music written to play, and to change while it plays

Numbers that move

▶ Open in Aratu to hear the examples, change them and do the exercises

A DJ turns the filter knob slowly and the whole dance floor feels the music opening up. A guitarist rocks the pedal and the sound sweeps back and forth. In Aratu a number can move on its own too, from one value to another, while the music plays.

From one value to another: ->

Write the starting value, an arrow, the value to reach, and how long it takes, with over:

Try it▶ Hear it in Aratu
tempo: 100
bass: synth.saw -> lowpass
bass = | c2 c3 c2 c3 | eb2 eb3 eb2 eb3 |
bass.lowpass.cutoff = 300 Hz -> 4000 Hz over 4 bars

The filter opens over four bars and stays open. Both numbers get a knob, and while it plays a second needle shows where the number is now.

The cutoff moves on the ear's scale: halfway between 300 and 4000 Hz it is at about 1100 Hz, not 2150, and that is why the sweep sounds even from start to end.

There and back: <->

With <-> in place of the arrow, the number goes there and back without stopping: it opens over four bars, closes over four, opens again.

Try it▶ Hear it in Aratu
tempo: 100
bass: synth.saw -> lowpass
bass = | c2 c3 c2 c3 | eb2 eb3 eb2 eb3 |
bass.lowpass.cutoff = 300 Hz <-> 4000 Hz over 4 bars

A different length on the way back, and starting over

Write What it does
A -> B over 4 bars goes from A to B over 4 bars and stays at B
A <-> B over 4 bars there and back, 4 bars each way, again and again
A -> B over 4 bars, back over 2 bars up over 4, back over 2, once
A <-> B over 4 bars, back over 1 bar up over 4, back over 1, again and again
A -> B over 1 bar, loop up, then from A again, like a ramp

A short loop makes rhythmic effects. Here the pad's volume rises on each beat and starts again, like a compressor "breathing":

Try it▶ Hear it in Aratu
tempo: 120
pad: synth.pad
pad = | c4+eb4+g4 _ _ _ |
drums { bd = b b b b }
pad.volume = 0.1 -> 0.8 over 1 beat, loop

The length can be in bars (bars), beats (beats), eighth notes (eighths) or sixteenths (sixteenths).

When it starts

Try it▶ Hear it in Aratu
tempo: 120
bass: synth.saw -> lowpass
bass = | c2 c3 c2 c3 |
drums { hh = cc cc cc cc; bd = b b b b }
bass.lowpass.cutoff = 400 Hz
every 4 bars: bass.lowpass.cutoff = 400 Hz -> 6000 Hz over 2 bars

Exercises

Make the filter open from 300 Hz to 4000 Hz over 4 bars.

Exercise▶ Hear it in Aratu
bass: synth.saw -> lowpass
bass = | c2 c3 c2 c3 |
bass.lowpass.cutoff = 300 Hz
See an answer
bass: synth.saw -> lowpass
bass = | c2 c3 c2 c3 |
bass.lowpass.cutoff = 300 Hz -> 4000 Hz over 4 bars

Now the filter goes there and back without stopping, two bars each way.

Exercise▶ Hear it in Aratu
bass: synth.saw -> lowpass
bass = | c2 c3 c2 c3 |
bass.lowpass.cutoff = 300 Hz -> 4000 Hz over 2 bars
See an answer
bass: synth.saw -> lowpass
bass = | c2 c3 c2 c3 |
bass.lowpass.cutoff = 300 Hz <-> 4000 Hz over 2 bars

At bar 3, the keys' reverb jumps to 0.6, all at once.

Exercise▶ Hear it in Aratu
keys: keys.epiano -> reverb
keys = | c4+e4+g4 _ _ _ |
See an answer
keys: keys.epiano -> reverb
keys = | c4+e4+g4 _ _ _ |
at bar 3: keys.reverb.mix = 0.6