Hey Julien,
as I have been deep into Lemur programming in common and especially into step sequencing, I like to add some words based on my experience through the years.
A midi step sequencer on Lemur only is not possible if it comes to some point of complexity and time accuracy.
That sounds harsh, I know, but it is really based on years of experience and tries....
The Lemur is great interactive controlling tool. Its possibilities to programm are amazing (and thats what makes the big difference to TouchOSC) and we have seen some wonderfull tools realized on Lemur only (Antonio...you are unbelievable!). However, don´t overestimate the possiblities of the Lemur (or underestimate the needs for a step sequencer).
The biggest problem is timing. Time on Lemur is based on framerates. And framerates are based on how busy the Lemur is - the more work your project has (based on how big it is, how many lines of code and how many interactions at that moment) the less accurate is the timing. To me Lemur timing was never even near being accurate enough for step sequencing - especially if it comes to drums. Sure, a few milliseconds more or less are quite normal with Midi anyway, but all results I had (with my own tries or modules of others) were unusable. Well... have a try... the best step sequencer on Lemur only (imho) is done by Sean Edwards:
http://liine.net/en/community/user-library/view/214/
The other problem is complexity. Step sequencers differ hardly in that point. I am a freak of control.... so I like to control (nearly) every aspect of a step. Not always, but I see it as important that I can control velocity and length (and much more like propability) of a step if I want to. Also I like independent numbers of steps and different grid for polyrhythmic attemps. Programming something like this on Lemur only - also including all pattern - would be a damn hard job. Not impossible....but as lines of codes may rise dramatic, timing will drop additional to the initial timing problem. So the simpler the sequencer is, the more realistic it is to get a tolerable timing.
Thats just my experience. Maybe I am wrong....
But it wasn´t voluntary or just for the fun of it that I digged my nose into max to realize my dream sequencer.
Hope that helps (although I know this answer might disappoint you)
All the best
mat
Lemur modules and sequencer:
http://music-interface.com
Setup: Win7professional 32bit, Intel Core 2 Duo @ 2,66 GHz.,Tascam US-144MKII, Ableton Live 8.4,
Arturia Analog Lab., Max/Msp, Maxforlive, Lemur Legacy + Ipad, Akai MPK61, Doepfer Pocket Control