I used to be in marching band; I did it because I was trying to impress one of the colorguards.
I eventually won her over (hooray!).
I will take a guess at your instrument and say either flute or clarinet.
On your question, it is pretty odd that you fall asleep while trying to PR. The only solution I can come up with is that you need to get more sleep. It sounds pretty silly, but as a person with bad sleeping habits(Mastermind will attest to this) I know I will fall asleep almost anywhere if I'm tired and my conscious mind isn't occupied.
For example, I think one kid for a science project stayed up for something like 11 days playing video games. He could do it because his conscious mind was constantly occupied (if you get tired and need to stay up, try to keep adding 7 in your head over and over again, or multipling by 3; it works for some people).
If you're pretty awake but driving down a highway for a long stretch, your conscious mind can get tired, and a lot of people fall under "highway hypnosis", which happens because of the repetition of the lines on the asphalt, the straightness of the road, and the same, low humming noise of the car on the road.
With PRing we are using our other than conscious mind, and letting our conscious mind take a break. If you're tired, I suppose this could lead to sleep.
Just theorizing, mind you.
-Ramon http://razor.ramon.com
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