For example, I use 34 Hip Hop or 28 Euro-beat and I just adjust the tempo to a slower one for them to recite their sounds as a sound rap to the beat. Once the other students finish, and there aren't many keyboards available, I gather them near the vocalization area of my music room and there I have another keyboard where i can play a certain register and have them listen to it.
I call on a smart music student to try on rapping his sounds to the beat, or I usually give them the cue when to start.
The students find this activity very cool. After which, I have them practice their sound rap, improvise, make different body percussion accompaniments and perform it in class where I'll have the chance to grade them and enjoy it myself.