In addition to uploading and creating your own songs, you can also edit existing songs.
If the song was originally created by you, you will see edit song and delete song options in the menu. Clicking edit song will open SongCreator so that you can edit the song. From the same menu, you can also add the song as your favorite or add it to a collection.
If the song was originally created by another user, you will see a Create copy option. Clicking/tapping it will open SongCreator where you can edit the song and save a copy of it. (You will not be making any changes the original file.)
If you edit songs made by other users by creating a copy, you will be prompted to provide a new name for the song when you save it.