rollout.rb

namespace :deploy do
  task :default do
    start_serenading
    transaction do
      # ....
    end
    stop_serenading
  end
end

desc "Start serenading"
task :start_serenading do
  fork {`afplay '/path/to/rollout.mp3'`}
end

desc "Stop serenading"
task :stop_serenading do
  system("killall -TERM afplay 2>/dev/null")
end