waltzize.rb

#!/usr/bin/env ruby
require 'rubygems'
require 'scissor/echonest'
require 'pit'

config = Pit.get('echonest.com', :require => {
    'api_key' => 'your Echo Nest API key'
  })

Scissor.echonest_api_key = config['api_key']

def main
  if ARGV.size != 2
    puts "usage: #$0 infile outfile"
    exit
  end

  infile, outfile = ARGV

  results = []
  Scissor(infile).beats.each_with_index do |beat, index|
    results << beat if index % 4 != 3
  end

  Scissor.join(results) >> outfile
end

main