This is a feature that iTunes had; you could change attributes of a song, and then save a new version.
This was especially helpful to raise the volume of a song permanently. I know you can temporarily adjust the volume in MB, but it doesn't permanently save it. E.g., the Eagles Hotel California album is notoriously quiet. With iTunes you could raise the volume and save it as a new version - and you could do this multiple times to continue to increase the volume. The song would now have the new volume levels when played across different devices (via different players).
Similarly, you could change the starting point or ending point of songs. This is helpful to eliminate delays in songs. But mostly, I used this to create custom ringtones that started at a certain point in a song.
I think you could also save custom EQ settings for individual songs. This allows you to effectively "remaster" songs.
If this "modify and save" feature already exists, I would love to know how to do it.
Thank you for your help!
But I also want to take this opportunity to compliment you all on this fantastic app!!!