Audio player for transcribing and taking notes of meeting recordings
I finally ended up using VLC player which provides (non-global) shortcuts for the required functions (e.g., ␣ for play/pause, ⌘+⌃+← for a very short backward skip).

I then used BetterTouchTools to allow invoking these shortcuts globally by adding new keyboard shortcuts that use the action send shortcut to specific app to forward the custom-defined global shortcuts to VLC.