ArrangeMe is currently developing the ability to support MP3 files as a for-sale product.
This feature will be completed after the migration of all PDF files from SMP Press to ArrangeMe.
In the meantime, you may continue uploading any new for-sale MP3 files to your old SMP Press account. All for-sale MP3 assets will be migrated at a later date once that feature has been added to the ArrangeMe platform.
(NOTE: This pertains to for-sale MP3 files only, not demo/preview MP3 audio which is a separate element and may be uploaded to ArrangeMe during the song registration process.)