The MPG64-R is a free Step Midi sequencer instrument and is the sister program of the MPG64-A and is geared for creating drum patterns. Some features include the ability to play in midi sync with the MPG64-A and the ability to export the pattern data to a Midi file.
The MPG64-A (Midi Pattern Generator 64 Alpha) is a free 64 step midi sequencer designed to run on Win 7, Windows Vista or XP with a minimum screen resolution of 1024×768.
Nova3 is a free VST Generative Sequencer plugin. The plugin is for Windows only, and includes an x32 and x64 version.
BlueARP is a free VST MIDI Arpeggiator with pattern sequencer style, designed for electronic music genres.
RPS-1 is a free pattern sequencing VSTi plugin designed primarily for the rapid creation of percussion sequences with random variations.