well, a lot of different ones tbh XD. so first, I get one shots and fx like snares, kicks, and so on from youtube that are copyright free, and others that people from AT have uploaded. Then, I search around other free-to-use online DAW's like Soundtrap, Bandlab, Soundation, and Ampedstudios, which I found out about very recently, and get even cooler fx's and drums. Then, I put them all together and make it, then bounce the timeline using AT's probe.