First, isolate the cymbal you want to choke by putting it on it's own track.
Then, if you want the cymbal to last only a 1/4 note long, wth a sudden stop on the last 1/16th note, try this
Lets assume you are using Reaper's default 960 ticks per quater note.
Fist, a disscusion on the difference between cc 11 and cc 7.
Controller 11 (expression) has values of 127 (all up) to 0 (off)
Also. remember that cc 11 is a subset of cc 7 (volume), so if your your overall volume is 100, than cc 11 at 127 has a volume of 100. cc 11 at 64 has volume of 50. and cc 11 at 0 has a volume of 0
Both CC 7 and 11 work in concert
Now go to your Daw event controler drawing pencil, and for a crash hit, start the the first hit at cc 11 - 127 for 720 ticks (the first 3 1/6 notes of the 1/4 note), than draw a 90 degree angle of cc 11 events from 127 to 0, starting from tick 720 to tick 960, and, wa la - a cymbal choke.
Importent: If you have lot of cymble chokes to perfome one right after the other, make sure that each cymbal has it's own track, since, when you raise the cc 11 back to 127, you might get the tail end of the previous cymbal.
Also, if your using a midi for an external module, it is impotant that you give rapid fire cymbal chokes, swells and fades their own track and channel #
Hope this helps,
Mondo
