i need a software program which will enable me to produce a track using loops and samples.

i use a mac so have garageband but it's not possible to stretch the loops so everything i sample and use will have to be identical tempos and played at their normal speed.

i used to use a program called acid music which was ok, the main benefit was it could do the above, but not great for other things.

i'm also ridiculously broke so if someone could recommend a free download or something that'd be great.