new_contents: # Copyright 2017 Google Inc. All Rights Reserved.
  #
  # Licensed under the Apache License, Version 2.0 (the "License");
  # you may not use this file except in compliance with the License.
  # You may obtain a copy of the License at
  #
  #    http://www.apache.org/licenses/LICENSE-2.0
  #
  # Unless required by applicable law or agreed to in writing, software
  # distributed under the License is distributed on an "AS IS" BASIS,
  # WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
  # See the License for the specific language governing permissions and
  # limitations under the License.
  """A MIDI clock to synchronize multiple `magenta_midi` instances."""
  import time
  
  # internal imports
  import tensorflow as tf
  
  from magenta.interfaces.midi import midi_hub
  
  FLAGS = tf.app.flags.FLAGS
  
  tf.app.flags.DEFINE_string(
      'output_ports',
      'magenta_in',
      'Comma-separated list of names of output MIDI ports.')
  tf.app.flags.DEFINE_integer(
      'qpm',
      120,
      'The quarters per minute to use for the clock.')
  tf.app.flags.DEFINE_integer(
      'clock_control_number',
      42,
      'The control change number to use with value 127 as a signal for a tick of '
      'the clock (1 bar) and a value of 0 for each sub-tick (1 beat).')
  tf.app.flags.DEFINE_integer(
      'channel',
      '1',
      '0-based MIDI channel numbers to output to.')
  tf.app.flags.DEFINE_string(
      'log', 'WARN',
      'The threshold for what messages will be logged. DEBUG, INFO, WARN, ERROR, '
      'or FATAL.')
  
  
  def main(unused_argv):
    tf.logging.set_verbosity(FLAGS.log)
  
    # Initialize MidiHub.
    hub = midi_hub.MidiHub(
        None, FLAGS.output_ports.split(','), midi_hub.TextureType.MONOPHONIC)
  
    cc = FLAGS.clock_control_number
  
    # Assumes 4 beats per bar.
    metronome_signals = (
        [midi_hub.MidiSignal(control=cc, value=127)] +
        [midi_hub.MidiSignal(control=cc, value=0)] * 3)
  
    hub.start_metronome(
        FLAGS.qpm, start_time=0, signals=metronome_signals, channel=FLAGS.channel)
  
    try:
      while True:
        time.sleep(1)
    except KeyboardInterrupt:
      hub.stop_metronome()
  
    print 'Clock stopped.'
  
  
  def console_entry_point():
    tf.app.run(main)
  
  
  if __name__ == '__main__':
    console_entry_point()
  
subject: Add missing midi_clock.py (#716)