topaz

MIDI syncable tempo in Ruby

Installation

gem install midi-topaz

Requirements

these will install automatically with the gem

Usage

require "topaz"

For demonstration purposes, here’s a mock sequencer class and object

class Sequencer

  def step
    @i ||= 0
    $stdout.puts "step #{@i+=1}"
  end

end

seq = Sequencer.new

The simplest application of Topaz is to create a clock to step that sequencer at a given rate. Using timing generated internally by your computer, the passed in block will be called repeatedly at 130 BPM

@tempo = Topaz::Tempo.new(130) { seq.step }

You may also use another MIDI device to generate timing and control the tempo. The unimidi input to which that device is connected can be passed to the Tempo constructor

@input = UniMIDI::Input.first.open # an midi input 

@tempo = Topaz::Tempo.new(@input) { seq.step }

Topaz can also act as a master clock. If a MIDI output is passed to Topaz, MIDI start, stop and clock signals will automatically be sent to that output at the appropriate time

@output = UniMIDI::Output.first.open # a midi output 

@tempo = Topaz::Tempo.new(120, :midi => @output) { seq.step }

Input and multiple outputs can be used simultaneously

@tempo = Topaz::Tempo.new(@input, :midi => [@output1, @output2]) { seq.step }

Once the Tempo object is initialized, start the clock

@tempo.start

If you are syncing to external clock, nothing will happen until a “start” or “clock” message is received

Other things to note

Whether or not you are using an internal or external clock source, the event block will be called at quarter note intervals by default. If you wish to change this set the option :interval. In this case, the event will be fired 4 times per beat (16th notes) at 138 BPM

@tempo = Topaz::Tempo.new(138, :interval => 16) { seq.step }

View the current tempo, which is calculated by Topaz if you’re using an external MIDI source. (this feature is currently in-progress and may return some low values - 5/26/2011)

@tempo.tempo
  => 132.422000

Run the generator in a background thread by passing :background => true to Tempo#start

@tempo.start(:background => true)

Pass in a block that will stop the clock when it evaluates to true

@tempo.stop_when { @i.eql?(20) }

topaz

Installation

Requirements

Usage

Other things to note

Documentation

Author

License