
"MRP Sequencer is a software step sequencer conceptually very similar to vintage analogue step sequencers such as the ARP 1601/1603 and Korg SQ10, and recent digitally controlled step sequencers such as the Frostwave Fatcontroller and Colin Fraser's P3.
MRP Sequencer goes a little beyond the feature set of most step sequencers.
sequences of up to 64 steps
track count limited only by processing power
output MIDI port and channel can be set per step
select-modify paradigm enables any set of steps to be affected by editing operations
extensive randomisation/variation functions
graphic user interface
text user interface enables full scripting"
Title link takes you there. Via Jason Proctor on AH.
Update:
Three more for the mac via Chris Muir on AH:
Roll your own in Max:
http://www.cycling74.com/products/maxmsp
Numerology:
http://www.five12.com/index.html
M from Cycling74
http://shopping.netsuite.com/s.nl/c.365211/sc.2/category.24/it.A/id.258/.f