clean-up #1:
two supercollider classes i wrote long ago (nov 2008) after a technique described by Godfried Toussaint in his paper 'The Euclidean Algorithm Generates Traditional Musical Rhythms'
also see for another implementation with some great demos. and Bjorn Westergard has a sc demo here.

lots of typical patterns in say techno music can be described like this using only two numbers (relation).

below is some example supercollider code with resulting output as mp3. the hihat plays a 9/16 rhythm throughout and the snare plays 3 different ones... 5/8, 15/16 and 3/8.

a=, "sounds/Free_CR68/CR68_BD_B_03.wav")
b=, "sounds/Free_CR68/CR68_SD_B1.wav")
c=, "sounds/Free_CR68/CR68_hh_02.wav")

SynthDef(\oneshotMono, {|out= 0, amp= 0.1, pan= 0, rate= 1, buffer|
        var src=, buffer, rate*, doneAction:2);,, pan, amp));

d= TempoClock(120/60)
Pdef(\bd).play(d, quant:4)
Pdef(\hh).play(d, quant:4)
Pdef(\sd).play(d, quant:4)
Pdef(\bd, Pbind(\instrument, \oneshotMono, \buffer, a, \dur, 1.00, \amp, 0.7))
Pdef(\hh, Pbind(\instrument, \oneshotMono, \buffer, c, \dur, 0.25, \amp, Pbjorklund(9, 16, inf)*0.7, \pan, Pbrown(-1, 1, 0.2, inf)))
Pdef(\sd, Pbind(\instrument, \oneshotMono, \buffer, b, \dur, 0.25, \amp, Pbjorklund(5, 8, inf)*0.3))
Pdef(\sd, Pbind(\instrument, \oneshotMono, \buffer, b, \dur, 0.25, \amp, Pbjorklund(15, 16, inf)*0.3))
Pdef(\sd, Pbind(\instrument, \oneshotMono, \buffer, b, \dur, 0.25, \amp, Pbjorklund(3, 8, inf)*0.3))

update 110316: adapted Pbjorklund to also take patterns as arguments.
update 110320: made a quark out of it

Bjorklund is now available as a supercollider quark. install it via the following commands...

//check Bjorklund, click save and recompile

or download and install it manually from here