I did the piano install earlier this week and it went well.

I used a small 4ch Mackie mixer that provided phantom power to the Barcus Berry contact mic.  The audio out for the accompaniment track was intercepted and passed into the mixer and then the tape out from the mixer was fed into a Sonos Connect.

The piano already had a bunch up audio equipment installed underneath along with a humidity control system which had a reservoir, blower, heater and some sensors so it was crowded but found places to keep everything out of site.

Finding good placement for the mic took some time.  The self playing piano mechanism makes lots of noises not really present in a standard piano.  The actuators for the keys and pedals created lots of clicks, pops and other sounds that aren't very evident listening by ear, but the mic picked them all up.  Finally found a spot that didn't pick up much noise and still had decent sound.

Connecting through the Sonos Connect wasn't too big of a deal.  I was worried because I didn't have Ethernet available and no other Sonos devices close enough for SonosNet so had to configure over Wifi.  Was getting audio dropouts at first and enabled compression which cured the dropouts but introduces a significant 1-1.5sec delay.

Found that the Connect had latched onto a far away WAP and had poor signal strength so added some MAC filtering into the WAPs to lock it onto the nearest device.  Once this was done, the audio dropouts stopped and with compression disabled there wasn't a dicernible delay even when I turned on the ceiling speakers in the same room as the piano.