SEQ541 – A Free Step Sequencer For OS X

SEQ541 is a free MIDI pattern sequencer for OS X.

The program is designed to be extremely flexible, all it requires is that you have an external MIDI device generating a clock and it will output notes in time to a pattern sequence you specify.


  • you can’t record patterns, only input them via mouse
  • 128-note polyphony
  • you can run as many pattern sequencers simultaneously as your CPU can handle
  • you can store as many patterns as you want per sequencer
  • while playing, transitions to the next pattern don’t occur until the current pattern is done playing
  • variable pattern length: 16, 32, 48 and 64 notes
  • variable note length: 16th note through whole note in 16th note steps
  • fixed note-on velocity 0x64
  • play/stop must be driven from an external MIDI source
  • MIDI clock must be from an external MIDI source
  • can drive any hardware or software MIDI device
  • can echo MIDI clock to the external MIDI device (for arpegio or whatever)


9 thoughts on “SEQ541 – A Free Step Sequencer For OS X

  1. This software appears to be 7 years old— which is not itself an issue, necessarily. The post makes it look like this is a new release, but at 7 years, — and a version number of 1.0, it doesn't appear to have much going on in the way of current or future development.

  2. Can't you build it on Mac OS? Maybe the MIDI implementation is the only problem and that should be not the greatest problem (assuming SEQ24's source code is reasonably structured). So, why don't you try and do it yourself?

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