Instructions
Select "Music Studio" at the game's main menu, and then choose "Recording Studio" on the next screen.
Pick the option to "Create New Song."
Choose a tempo speed for your track, and add a bass line and drum tracks if you desire.
Connect the microphone or plug a headset into your Xbox 360 controller. Select the "Mic" option from the instrument list.
Use the control pad on the controller to operate the controls. Press "Right" to begin the recording and "Left" to rewind to an earlier portion of your track. Press "Right" a second time to stop the recording.
Save your track by pressing "Start" and choosing that option. From this menu you can also access the mixer to adjust the volume of accompanying instruments, as well as add new instruments to the mix.