Don't Drop the Bass - Source code with comments - Brighton Ruby 2017

dont_drop_the_bass.rb

# ❤️ Brighton Ruby

# This code uses some features from the pre-release of Sonic Pi,
# due out later this month (touch wood!).

# If you just can't wait for the release but want to try it yourself
# you can either build the Sonic Pi master branch from source (pros: free, cons: hard)
# or share some love and contribute to the Patreon page to support Sonic Pi's development
# https://www.patreon.com/samaaron
# That will give to access to the latest pre-release versions

# for anything I don't explain (like tick)
# click the Help button in Sonic Pi (top right)
# and check out the tutorial for more info

# four to the floor
use_bpm 100

# use_real_time is a new method in SP v2.13
# instead of using a sched_ahead_time to allow events
# to be sequenced in time, use_real_time just tried to
# schedule the events as quickly as possible.
# That means *some* latency, but not much.
# Which makes playing along with a real instrument more feasible.
# Anything over about 40ms latency and it starts to become really
# hard to play along.
use_real_time

# This live_loop sets up the bass drum
live_loop :bd do
  
  # lpf = low pass filter
  # the range.mirror is a kind of poor man's LFO
  # It's like turning the treble knob up very slowly,
  # then down very slowly over and over again.
  # The 80 and 110 are midi notes, corresponding to
  # roughly 800Hz and 5kHz
  sample :bd_haus,
    lpf: range(80, 110, 0.5).mirror.tick(:bd)
  
  
  sleep 1
end

# live_sample is a helper method I defined myself
# available here: https://gist.github.com/xavriley/b5f925daa1195dc6ef686297a3016c3d
# :bass is a label for the sample I'm about to record
# dur: 16 means it lasts for 16 beats
# sync: :bd means it starts on the next :bd loop
# check out cue and sync in the docs for how that works
live_sample :bass, dur: 16, sync: :bd


live_loop :groove, sync: :bass do
  
  # After recording the 16 beat bass loop,
  # here I was mostly messing around with the slice
  # and rate params to generate new/random basslines.
  # The on: param also helps to give it some rhythm
  # beyond just being a stream of random notes.
  sample buffer(:bass, 16),
    slice: rand(2),
    num_slices: 32,
    lpf: 90,
    rate: [1,-1].choose,
    on: spread(5,64).tick
  sleep 0.25
end

# Here I set up four short loops layered on top of each other
# with the following notes
# G  -> Bb
# D  -> F
# Bb -> C
# G  -> Bb
# This creates a kind of Gm7 chord to work with.
# I can then use stretch: 1 and the pitch: param
# to pitch shift this to other chords, Cm7 and Dm7
# Cm7 is 5 semitones above the original key of Gm7
# Dm7 is 7 semitones above the original key of Gm7
# knit(...) says don't transpose for 4 loops
# then transpose up 5 semitones for 2 loops
# then transpose up 7 semitones for 2 loops etc.
4.times do |n|
  name = "cascade#{n}"
  live_sample name, dur: 4, sync: :bd
  live_loop "groove#{n}", sync: name do
    with_fx :slicer, probability: 0.1 do
      sample buffer(name, 4),
        amp: 0.75,
        lpf: 70,
        rate: -1,
        stretch: 1,
        pitch: knit(0,4,5,2,7,2,5,2,7,2).tick
      sleep 4
    end
  end
end

# With those chords above (Cm7, Dm7 and Gm7)
# they all fit underneath one type of scale - the Bb major scale
# Another (fancy) name for that is G minor aeolian
# Here I setup the input from the bass using live_audio
# and some heavy compression and distortion to get that long
# sustaining sound, with some reverb to make it less harsh
with_fx :reverb, room: 0.8 do #octaver is good too
  with_fx :distortion, amp: 0.07, mix: 0.8, distort: 0.99 do
    with_fx :compressor, pre_amp: 5 do
      live_audio :basssolo
    end
  end
end