App to play music NAS > Minimserver > iPhone via headphone socket

[Alandbush]

Glider can sync music tracks from multiple music servers at the same time. These servers could present metadata differently, which is why Glider provides its own unified interface. Naturally, you do lose each servers tailoring options.
However, it’s a fairly new app and is still being developed.

FWIW it does gapless playback.