There are now some fantastic microphones for iOS which yield excellent quality recordings. For anyone, make sure that your acoustics are good in the room and your background is simple. Singers need a to have the piano recently tuned, but the panel honestly doesn’t care about the"size or color" of a kid’s voice- they know that they’re hearing a 17-18 yr old and are listening for potential not whether the kid can be heard in the back of a 3500 seat house the next year.