Problem with swipes is that you need to carry a manual and, eventually, you will do something bad by accident.

How about power wheel interface? It would be swipe-like.

Hold thumb in center of - say - artwork. After 1 second, a power wheel pops up (round menu, with 8 buttons, N, S, E, W, NE, etc). Each would be large enough to have a big icon and a small text underneath that one only needs to read once.

For example, buttons could be:
Left: delete from current playlist
Right: add to playlist ... (pops up list of playlists)
Top: Edit artwork
Bottom: Cancel

Then add more as needed to the said wheel. It's menu-like, but can be operated by thumb. Say, bottom left and right could be next and previous song or something (though they already have buttons).

You could have the wheel be hold-and-release or push-select, like menus are on your average desktop (I'm on Windows, so, disclaimer).

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Another idea is to reserve a swipe for a menu. For example, swipe down pulls the menu as if another window is above it, a la fcamera. Mighty useful and intuitive. It could be the same feel as the rest of the player has, with big menu bars and nice icons. Add to playlist, delete from playlist, etc. Swiping up would pull another window from below, that could be the current playlist, to jump songs.

Some work would be involved, but I believe this to be a great UI approach. You could tuck the artwork window to the left and so on.