I decided to use "motifs" in two different ways in Worms Blast: one for major game events, such as losing a life, triggering a firestorm, triggering double-damage mode, etc., and another one for minor game events, such as picking up a crate, gaining some extra health, hitting a target, etc.
I used motifs to react to minor game events. We had nine different motifs, each containing just a few notes with bright, sparkly instruments so that they would cut through the mix and be heard even if there was a lot of stuff going on in the background music. I set the motifs' boundary settings to Beat so that they would play in time with the music, starting from the next quarter note. This ensured that the motifs would play almost instantly but still not fall out of the rhythm set in the background music.