Hallo, bstine@telus.net hat gesagt: // bstine@telus.net wrote:
I know this is a little off topic, but this seems like the best place to ask. I was wondering what the best way to implement a sequencer is. I know that's a big question, but I mean in the most abstract way.
It is indeed a big question. There are several approaches to sequencing in general, some are also used in Miller's Pd docs and of course in his book (http://crca.ucsd.edu/~msp/techniques.htm) in the chapter on control computations. In the RRADical sequencers mentioned here I took a very simple approach, which is limited to pop music in 4/4 and with constant beat dvisions: I just divide a beat into 16 or 32 event slots, which are visited by a counter. If there is an event stored, when the counter hits a specific slot, it is output. Events can be one or two numbers in the current sequencers. This looks like:
slot ev1 ev2
0 60 127
1
2 60 0
3 40 75
...
16 60 127
Then I just use many of these to build real patterns.
Note that this is indeed very limited. A better approach IMO is to introduce a more general notion of an "Event" and then store the time of occurence or the so called Inter-onset Interval. The IOI is more popular in computer music I think, as you can do a lot of fine calculations on it, like scaling the IOI will make a sequence run in a differnet tempo etc.
[qlist] uses IOI times and can be used to record and playback events. However it's hard to get at the data stored inside a qlist to do funkier things. To find out the IOI between two events a
[t b b] | | [timer]
has proven to be very reliable.
Miller's data structure sequencer in the data structure examples is also somehow using IOI internally. The data structure events use x-position as onset times, but then Miller calculates the actual IOIs to drive a [delay] to the next event.
Data structures are really nice to do sequencing. You can put a lot of data, not just note and velocity, into the structure, position it and play it, do transformations by traversing all notes etc.
An example on how to record into a data structure windows is here: http://royalrabbit.goto10.org/svn/goto10/pd-patches/fbar/pipeseq/
Instead of using a data structure window to store a sequence, in other patches I also used the h_list and h_map externals from PDConainter for sequencing. They lack the graphical appearance, but have some other nice features. The basic idea there is to either [timer]-tag rows in a [h_list], then sent the complete list to [pipe], or use a [del]-construction similar to the data structure sequencer which uses IOI times. This is more flexible if you want to to stuff like tempo changes while a sequence is playing - which never happens in techno music so there all this unnecessary anyways.
For reading about this stuff, I can for example recommend Robert Rowe's "Machine Musicianship" at MIT Press, IIRC.
Ciao
Frank Barknecht _ ______footils.org_ __goto10.org__