A:AnswerAnswering my own question: There are two Yamaha apps available by slightly different names, one that relies on Bluetooth and one that relies on LAN (SR-C20A has no LAN capability). I was failing because at first I out the wrong app on my iPhone.
A:AnswerYou must use the sound bar remote. Optical connectors only send the digital version of the sound and cannot control volume.
I recommend using a universal remote that will control all your devices.
A:AnswerHi. This soundbar has HDMI ARC, Optical, AUX/analog audio input ports + bluetooth. Traditional CD players that use RCA/composite audio output are not compatible, unless connected to a female RCA to male AUX adapter. Portable Walkmans with AUX output port will work just fine.
A:AnswerAll the information you could ever need for this product can be found here:
https://www.crutchfield.com/S-WU3FJDsLDCP/p_022SRC20A/Yamaha-SR-C20A.html#:~:text=Product%20highlights%3A%201%20two-channel%20sound%20bar%20with%20simulated,6%20listening%20modes%3A%20stereo%2C%20standard%2C%20movie%2C%20and%20game