Ableton Live is one of the best in my opinion if you want to record sounds and create songs (more than just mixing). The "bad thing" is that it's not free.
I think you're probably looking for a free app, so this probably doesn't help you a lot, but is what I can share about that ^^ :
I used Ableton long time ago to make music and some BSO for shortfilms using beats from internet and making my own sounds, recording piano, guitar and other sounds (some crazy folleys I was asked to do, don't ask please xD). Also I tried so many softwares as Pro Tools or Reason in different jobs but for what you're talking about I found Ableton the best one.
Now I don't play the any instruments, I don't create songs neither make any strange folley, visual arts eat all my time xD But some of my friends that are working in the industry are using it so I think the softs still similar than before.
All depends in what you're looking for, same as 3D softs , if you want just to try and play the piano , probably they're some free softs better for it. Audacity I think is one of the most famous but I don't know if it works well for mixing but I'm sure there are some easier apps as the one cedricgo says to just play the piano while playing some beats.
You can try Ableton for free 30 days, and they have an 80€ licence, but look well if you're going for it couse probably you can't do something you want with this short licence.
Hope it helps (I think not a lot) at least a little "beat"... omg, ok, I stop here. ^^
Let us know what you finally did!