Without question, the biggest challenge I face developing classes on music is what will end up being on the playlists. Doesn't matter if it's a brief presentation or multi-day course, it's exquisite torture every time.
I've also observed that as soon as my playlist falls into place, alchemy occurs. Unfortunately, that pushes up against my training as an educator. I was always instructed that content - a playlist would fall under that heading - should flow from teaching objectives, not the other way around. And though it's likely those objectives are in my head - even as I'm combing through my collection, trolling I-tunes and soliciting input from others for the playlist - if I haven't written them, well, they're not real objectives then are they? Meanwhile, precious time ticks away as I try extracting my rule-bound head from an otherwise enjoyable process.
In the end, the torture, the alchemy - even the confounded objectives - bring me such joy that raising the issue feels a bit churlish. Maybe if someone else on the bell curve told me they've ever struggled with a tension between alchemy and education, I'd feel better?