Hi. I am using Ableton Live on a Mac. I have accidentally saved a over song/project with another song/project. Is there any way to recover the original song/project? (I dont use Time Machine!)

Unfortunately Ableton does not make a backup folder with older projects.. So it sounds like you have saved over the project. Definitely put some backup process in place to avoid things like this in your future productions. I would recommend a Time Machine backup as you can go 'back in time' and recover files you have overwritten.