Sonic Pi Part Two — Structure/FX
Recap
In part one we looked playing synthesised sound and samples. Here we will expand and introduce some more structure/patterns and look at FX.
- Loops and iterators — to introduce some basic structure
- Randomisation — to introduce some more interesting sounds
- Effects — Overlaying some FX (a reverb effect) to the samples
- Generating arpeggios — using some variables and loops
Loops/Iterators
In part one we used a simple loop to play a set of kick drum samples, this was as follows:
use_sample_bpm :drum_heavy_kick
4.times do |n|
sample :drum_heavy_kick
sleep 0.5
end
Let’s expand on this by:
- Playing a sample (A bass drum kick) a specific number of times (using .times)
- Adding another sample which plays after the first, we’ll use the sleep keyword to play it at a slower speed.
use_sample_bpm :drum_heavy_kick
4.times do |n|
sample :drum_heavy_kick
sleep 0.5
end3.times do |n|
sample :drum_heavy_kick
sleep 2
end
Now let’s surround the whole thing in an infinite loop so it repeats until further notice:
use_sample_bpm :drum_heavy_kickloop do
4.times do |n|
sample :drum_heavy_kick
sleep 0.5
end
3.times do |n|
sample :drum_heavy_kick
sleep 2
end
end
Use ⌘ + R shortcut or use the “Run” button. This time you will need to use the ⌘ + S shortcut or use the “Stop” button.
Pretty cool? Try playing about with the values for sleep, add another .times section. It’s interesting to try and emulate something you know in popular music.
Ok, lets go back to a synthesised instrument and look at some basic algorithms.
Randomisation
We can use any synthesised instrument and use a function called rrand() to generate a different note each time. Ends up sounding somewhat eerie.
use_synth :pianoloop do
play rrand(20, 80)
sleep 0.1
end
You can also apply rrand() to other things, try using it with the sleep keyword.
Effects (FX)
Whilst we’re at it, lets use some Sonic Pi FX (reverb)to make our odd piano loop sound even weirder:
use_synth :pianowith_fx :reverb, room: 0.9 do
loop do
play rrand(20, 50)
sleep 0.4
end
end
You can find out more about FX parameters here:
And also the reverb FX with the various parameters here:
Generating Arpeggios
Ok. So we’ve generated some basic sequences of notes. Now let’s look at a fairly standard structure in music – the arpeggio. We do create an arpeggio by cycling through an array of notes and altering the base_note value in the following (first by adding 3 to it and then by adding 7). We do this for every note in the array by incrementing n by 1.
interval = 0.2
notes = [72, 65, 58, 62]while true
n = 0
notes.length.times do
base_note = notes[n]
3.times do
play base_note
sleep interval
play base_note + 3
sleep interval
play base_note + 7
sleep interval
end
n += 1
end
end
That gives you an ascending arpeggio. Try creating a descending arpeggio by subtracting from the value also.
We should now have some very basic building blocks for creating sequences. We could improve the structure further by using functions, but this is good enough for now.
In part 3 we’ll look at building a song out of synthesisers (for drums, base and melody) and then add some Sonic Pi samples for variety.
Cheatsheet
https://www.cl.cam.ac.uk/projects/raspberrypi/sonicpi/media/sonic-pi-cheatsheet.pdf