KMidiTracker is a MIDI Step Sequencer for ALSA similar to FastTracker or Buzz, but only the tracker part, as the output is only MIDI data that can then be used by any kind of synthesizer.
Introduction
  KMidiTracker is a MIDI Step Sequencer.
  A Step Sequencer is a sequencer in witch the MIDI notes are delivered 
at regular time intervals, usually a 1/4th of a quarter note. As such it 
is not as versatile as a regular sequencer as [Rosegarden], but allows 
very easy creation of loops and sequences. The use of the [MIDI Clock] 
allows several sequencers communicate clock events, so it is possible to 
join several sequencers, with diverse focus, to make one single 
synchronized composition.
  KMidiTracker is similar to trackers like [FastTracker], 
[ScreamTracker] or [Buzz], but only the Tracker; no actual sound is 
emmited. Only MIDI signals.
  The Tracker divides songs in tracks, each one have several patterns 
that are arranged as sequences. Time advance in steps that depend on 
tempo, and in each time step a new MIDI note may sound, or a controller 
event may be sent. You can have several columns of notes and/or 
controllers for each pattern, and pattern length is configurable.

KMidiTracker Features

* MIDI oriented Step Sequencer
* ALSA MIDI input/output
* Keyboard input
* Graphical Controller edition
* Controllers include MIDI Controllers, SysEx Controllers and PitchBend
* MIDI Master Clock (master and slave)
* Linux RTC timer or MMC if avaliable for perfect timing
* Tracks and columns in patterns muteable
* SysEx parameters. Can be loaded from binary file, manually inserted in 
      hex, or captured from midi input.
* Variable Time Signature
* Load/Save
* KDE application: easy menu, toolbar and shortcuts changes
* Everything can be changed in realtime: notes, arrangement, loops, 
controllers, load/save, new tracks or patterns, delete tracks or 
patterns...
* GPL license