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Forked from emlyn/guitar.rb
Created May 28, 2018
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Strumming guitar chords in Sonic Pi
# Guitar Strumming - by Emlyn
# This tries to work out the guitar (or ukulele etc.) fingering for arbitrary chords (and tuning).
# It seems to work reasonably well for basic chords, but is quite naive and probably makes many mistakes.
# Ideas, bug reports, fixes etc. gratefully received, just comment below, or tweet @emlyn77.
# Feel free to make use of this code as you like (with attribution if you feel like it, but you don't have to).
# Thanks to @Project_Hell_CK for fixing the tuning, and spotting that it gets chord(:f, :major) not quite right.
# Next note higher or equal to base note n, that is in the chord c
define :next_note do |n, c|
# Make sure n is a number
n = note(n)
# Get distances to each note in chord, add smallest to base note
n + ( {|x| (note(x) - n) % 12}).min
ukulele = [:g, :c, :e, :a]
guitar_standard = [:e2, :a2, :d3, :g3, :b3, :e4]
# Return ring representing the chord chrd, as played on a guitar with given tuning
define :guitar do |tonic, name, tuning=guitar_standard|
chrd = (chord tonic, name)
# For each string, get the next higher note that is in the chord
c = {|n| next_note(n, chrd)}.ring
# We want the lowest note to be the root of the chord
root = note(chrd[0])
first_root = c.take_while {|n| (n - root) % 12 != 0}.count
# Drop up to half the lowest strings to make that the case if possible
if first_root > 0 and first_root < tuning.count / 2
c = (ring :r) * first_root + c.drop(first_root)
# Display chord fingering
#puts {|n, s| if n == :r then 'x' else (n - note(s)) end}.join, c
# Strum a chord with a certain delay between strings
define :strum do |c, d=0.1|
in_thread do
play_pattern_timed c.drop_while{|n| [nil,:r].include? n}, d
use_debug false
use_bpm 120
live_loop :guit do
#chords = ring((guitar :d, :m7), (guitar :g, '7'), (guitar :c, :M7), (guitar :f, :M7),
# (guitar :b, :m7), (guitar :e, '7'), (guitar :a, :m7))
chords = ring((guitar :a, :m), (guitar :c, :M), (guitar :d, :M), (ring :r, :r, 53, 57, 60, 65),
(guitar :a, :m), (guitar :c, :M), (guitar :e, :M), (guitar :e, '7'))
with_fx :reverb do
with_fx :lpf, cutoff: 115 do
with_synth :pluck do
"D.DU.UDU".split(//).each do |s|
if s == 'D' # Down stroke
strum chords.look, 0.05
elsif s == 'U' # Up stroke
with_fx :level, amp: 0.5 do
strum chords.look.reverse, 0.03
sleep 0.5
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