In case you ever wondered how to create an 808 kick in ruby

808-kick.rb

# consult the signal flow graph for a ringing digital filter at
# http://i.stack.imgur.com/49pxl.jpg

require 'wavefile'

Frequency = 50
SampleRate = 44_100
DecayFactor = 0.15

fc = 2 * Math.sin((Math::PI * Frequency)/SampleRate)
tc = Math.exp(-1/(SampleRate * DecayFactor))
d1 = 1
d2 = 0

include WaveFile

samples = []
50000.times do 
  output = d2 + (d1 * fc)
  d1 =  (d1 * tc) - ( output * fc) 
  d2 = output
  samples << output
end


Writer.new("kick.wav", Format.new(:mono, :pcm_16, 44100)) do |writer|
  buffer_format = Format.new(:mono, :float, 44100)

  buffer = Buffer.new(samples, buffer_format)
  writer.write(buffer)
end