Recording apps for iPhone

[uh-oh]

do you have a computer?

you are better off recording into your phone with headphones on so the phone doesnt record the beat, just your acapella.

then on a computer, open any recording program, put the beat in there and then bring the verse acapella from your phone and re-line it up

to help lining it up you can clap when the beat drops, or during something in the beat before you start spitting, and you can line where you clapped up and then just edit you clapping out

im still anti-smart phone and got the cheapest most generic one so i cant help in the app department