You can distribute singles, EPs (extended plays), LPs (long plays), compilations, and any other audio recordings that you have created.
You can also distribute modern orchestral pieces you own, so long as you're able represent them correctly. E.g. You should be able to fit your release data into the Release Title, Primary Artist, Featured Artists and other fields when creating your release.
Music stores recommend selecting 'New Age' as the genre for these types of releases.