Set up a uPNP renderer on a RPi like this
http://blog.scphillips.com/2014/05/playing-music-on-a-raspberry-pi-using-upnp-and-dlna-v3/

and use one of the uPNP controllers on your tablet/phone (my current pick is BubbleUPNP although it's not free) in conjunction with Plex or whatever uPNP server you can install. I have Plex server running on unRAID so it's the full Linux version as compared to Synology where it might be a bit cut down. Certainly is no configuration required after initial setup for me (all via a web interface)

Still requires a tablet or phone to select and press play.