I'm very pleased to hear from you.
I will try to answer your questions as best I can.
For my present needs, I have been able to work out nearly all the questions I asked in my early post and referred to in your post just written:
1) Plugging the earphones into the socket beneath the control panel also renders the piano silent.
2) I will try the RCA cables when I need to play an accompaniment file, but I don't yet create accompaniment files. Presently I use the USB to midi-in connection – otherwise the iPad allows me to demonstrate audio accompaniment from files supplied with the piano. I have copies of early Yamaha discs used in the 850 controller. They are in .wav format in my computer which I had hoped to play thru the Enspire, but I am told that copy protection will prevent that type of use, although connecting any CD player unit via RCA leads should permit these discs to play thru the Enspire.
3) I have a Mac Computer which has Garage Band as an App. I drop the midi into Garage band and then, from 'Share' in the drop down menu, I can burn it to a blank CD. ALTERNATIVELY, if you are on PC, get hold of a short male to male 3mm stereo lead and patch from earphone socket directly into record socket of your computer. Play the midi in your computer (I double click the midi icon and RealPlayer automatically opens and plays it using sound fonts found in the computer). Plugging into the headphone socket will send the audio of the playing midi over to the record channel and, providing you have an App which will record sound, an audio recording will be created which you then burn to CD.
4) & 5) MusicCast has yet to be hooked up by me. I have all the necessary hardware components, but have not yet worked out how to connect them together, despite some instructional videos being available on YouTube. There has been no imperative for me to do it yet. In Sydney, Australia, we have Geeks2U which is a service provider which sends technicians for an hourly rate who can get these modern wireless systems working and interacting. I will use them when I feel the need to get everything connected. I'm sure that you would find an equivalent in California. You have the added advantage of being able to receive and record regular 'live' concerts on-line which will play thru your TV and stereo systems, simultaneously playing your piano which is the sort of incentive I need.
Do you use an editor to optimise your midis for playback? I think it is essential for anyone with a Disklavier, playing midis not made for their piano. Even files downloaded from Yamaha Den, can be uncomfortably forceful in playing back on the Enspire: Note velocities in some of these XP files are too strong and too loud for safe playing. I play everything through an editor to get sound levels correct for my piano in my room, and, having saved the adjusted file, then drag it into a Playlist created by QMidi. The optimised midi files are ultimately stored in a folder on my desktop, labelled "Midis Optimised for Yamaha".
I would like to hear from you as to how you use your Enspire and what you play on it. My great delight is in optimising emulations extracted from reproducing piano rolls.
Thank you for taking the trouble to write to me.