What sort of budget are you working with? How far are you going to be away from the subject? Since you are starting out, i will not reccommend anything too high-end because it may be more than you need. A very good tele-zoom in the $550 USD range would be the EF 70-300 f/4-5.6 IS. Great amount of range, good image quality and has Image Stabilization for sharper pics at low shutterspeed. A bit of a small aperature for dim lighting, but anything larger will cost you twice as much.
I take it the recital is indoors and lighting will be a major concern to try and get a good shutterspeed. To get anything over 1/250 without a flash will be a feat. So tinker with your ISO setting till you get a usable shutterspeed. Probably about 800-1200. The rule of thumb is that the shutterspeed should be 1/ (the focal length). The faster the better as long as the exposure is correct. With the IS you can get good results at much slower speeds, like 1/30, but it will not stop "action" shots. Only a fast shutterspeed can do that. Hope that helps.
