Well...I'll be the grumpy old man today...
Having attended games in both the non-PA-music era and blaring-PA-music era, the latter just gets really lame for me. It just seems to kill the natural crowd energy, and I actually find it distracting. But, I suppose in today's era of "long" commercial breaks, things like that are necessary to hold people's attention.
Back in the day, two courses of the school song and 30 seconds of the Hamm's Beer clap could pretty much kill a time out. The unison single-clap was pretty awesome, because pretty much everybody participated, and it was simple enough that pretty much everyone could get the timing down, regardless of their musical ability.
The clapping-out-of-time thing isn't unique to ISU. Some folks just aren't blessed with that ability. Seriously, it is really difficult for some folks, and because of that it is going to be tough to get everyone clapping on the right beat to a fast paced song.