There have been many discussions about alternative sequencer firmware that differs from the MBSEQ as written by TK. So far, only the SID 303 mode has developed into a finished product. Of the others, the vX and the beginner's 16 step have the most active work at the moment.
Here is an attempt to summarise and collate those discussions.
Strictly MIOS alternative sequencer thread - a summary of ideas to mid-2004
An 8 step sequencer - using TTL components and no PIC
MS-DOS/Linux sequenzer for old Laptop?
supersequencer? - diverged into DOS/Linux on SFF hardware discussion
Sequencer vX - stryd_one's MIOS algorhythmic pattern sequencer
MIOS Beginner's 16 step seq project - xOx style, MIOS code
trsequencer - summarise the features of the classic Roland TR style drum sequencer with intention to reproduce in MIOS
|Tap in a sequence? - tap tempo in the SEQ or with an external CORE
The MIDIBox SID also contains a wavetable sequencer, which can be used as an arpeggiator, or in 303 mode as a 3 track, 32 step sequencer. Use of the sequencer requires either JSynthLib or the 303 control extension and the alternative v1.7303 firmware.
The MIDIBox FM also contains the 3×32 wavetable sequencer