Yes, you CAN sing with instrumentals as well as not singing with instrumentals!
1. Locate song on MP3 player (iPod, etc.)
2. Play song on MP3 player and instrumental on computer.
3. Start recording and sing. The music plays, and no one can hear it but you, and all the audience will hear is your singing and instrumental.
4. ?????
5. PROFIT!
Also, Lee, couldn’t hear you. :/