I have weighed the benefits and risks of letting him play around with our CD player (benefit = at least several minutes of quiet play; risk = destruction of equipment) and for now have chosen to let him play around, being watched by either me or his dad, in the interest of building his engineering and observation skills.
I recently observed him in action and will replay the scene, action by action, for you here. We now embark on some variation of this adventure at least once a day:
2-3 CD's of kids' music
1 small CD boombox
1) K. picks up CD #1.
2) Opens the lid of the boombox.
3) Spins the CD around with his hands in the boombox (keeping the lid up so he can watch it spin).
4) Picks up CD #2, removes CD #1 from boombox.
5) Repeats steps 2-4, now picking up CD #3.
6) Opens up the case for CD #1.
7) Places one of the CDs (take your pick) into CD #1's case.
8) Before closing the case, takes a second CD and tries to squoosh it also inside the case.
9) I point out to him that he might scratch the CDs this way.
10) I show him the little raised bubble that helps anchor the CD in place inside the case.
11) He picks at the bubble, saying "Off, off!" and trying to get it off. I tell him it can't come off.
12) He takes both CDs and attempts to put them in the CD boombox at the same time.
13) I tell him we can't do this lest we scratch the CD (see step 9).
14) He removes one of the CDs, keeps the other in the CD boombox, and spins the CD with his hand, like an old fashioned vinyl record, repetitively.
15) Repeat any of the above steps in random order, depending on K.'s mood.
I'm either grooming a future DJ, or a repairman! Or both.