I think of reverb as a way to add a majestic or distant feeling to a sound.
So basically, it's an echo effect. Not to be confused with the delay effect.
(Reverb makes sounds seem like it's in a long room, on the opposite side than you.
Delay is the actual echo, playing the sound again but at a lower volume.)
It's good to add reverb to sounds that stop suddenly, like your whistle sound.
Adding them to drums... I tried that in my early songs before I knew how to add bass,
and it didn't turn out well. xD
But yeah, experiment with reverb and delay, it will make sharp-ending sounds seem more
powerful. o/