Midibox SEQ V4
The MIDIbox SEQ v4 is a very affordable DIY pattern-based sequencer, designed by Thorsten Klose. It has 16 simultaneous tracks which can be edited live. It runs on the Discovery STM32F4 processor. Typically built with four MIDI outs and up to four MIDI ins. A CV/gate/Trigger breakout gives eight CV/gate pairs and up to 64 triggers..
The MIDIbox site (ucapps.de) has information on how to build the Core and Midi I/O modules. Useful MIDIbox forum posts include Building a MIDIbox SEQ V4 (Wilba Control Surface) – Photo Tutorial, Wilba's MB-SEQ Construction Guide and Lasercut Acrylic Case+ Frontpanel for SEQv4.