DISCLAIMER: This post does mention another app. I am not advertising, because Caustic clearly surpasses GarageBand. I am simply stating the fact that they are a beautiful thing when combined. Also, CloudConvert isn't a music making app, it is very helpful for this though.
Are you an iPhone user with no access to a computer? Do you want to share your song or get it as an mp3 file? Do you want to make a complex song that changes tempo, or uses more than 14 instruments? Well then I have an amazing discovery for you.
Did you know that GarageBand is able to connect with Caustic? Did you know that GarageBand can take your Caustic tracks and open them in other apps? With the beautiful capabilities of song-making in Caustic, and the exporting options of GarageBand, you can share your music without a computer!
You can also combine Caustic songs! So let's say you make an extremely complicated verse for a song, but you took up too much space for the rest of the song. Simply save that verse, and then make whatever you want next in a different song file, then combine them in GarageBand! Then you can go back to the verse, change it however you want, and reuse it if you want to!
Then you can rename the track IN GarageBand, open it in another app (such as CloudConvert [free as well]), convert it to mp3, and then share it however you want!
Once again, I am not advertising for other apps, I'm just giving some options to people like me :P