Nov 09, 2012 03:27 pm
Well, assuming you have the instrumental as say, a wav file, or an mp3, you'll need to load that file in some software. Usually something like a DAW (Reaper, FL Studio, Cubase, etc.) This would be the backing track, and you would create a new track alongside it as the vocal track, set it to armed and make sure it is listening on whichever input from the 2i2 that your mic is connected into.
Then simply hit record, and start rapping to your beats and instrumentals.
I would suggest something like Audacity as a simple recording program, but I don't think it can load one track as playback while recording the vocal overdub to a new track. Reaper and any other DAW is certainly capable of doing the job.