I remember from way back when Robert A. Penfold had written some article in Practical Electronics Magazine about controlling the pitch of an instrument using hand movements. It wasn't using IR, but RF field modification by the moving hands. I cannot remember the exact name he used for it right now.

If you plan on using IR, Sharp has some sensors that could be useful. However, I am not really sure if they are the GO-NOGO type which work to a particular distance. One such sensor is the GP2Y0A02YK0F. It shows a range of 20-150cm and a nice curve to go along with it.

My hunch is you might be happier using near field RF for your application.