Do you know of a music making software?

I need to know about any music makers you know of. They need to be able to create and save music (notably piano, but I would appreciate being able to make other music) on the computer. Open-source or freeware is preferred to trial software or software that you have to buy. (I need something that doesn't require winRAR as I do not have it.) It would be very much appreciated if someone could help.