I have a violin performance and a piano performance chosen. My question to the experts out there is what is a good way to do this?

Yes there is.

You will want to “merge” the violin Performance and the piano Performance creating a New Performance that contains both instruments.
You would then setup the MONTAGE Performance Recorder (set Tempo, Time Signature, etc...) record the violin portion of the composition.
Next you would setup so that while the Sequencer plays back the violin portion of the composition, you can play along, live, using the piano sound you have selected.

That is one way to accomplish your goal. The steps to do it are best outlined with the specific Performances you’ve selected. There are details to consider when “merging” instruments into a Performance (let us know, if/when you run into any of these).

Start by recalling the violin Performance and work out the musical portion... From the HOME screen of your violin Performance:
Press the RECORD button
You will be taken to the Performance Recorder screen and you will be incremented to a new (empty) Sequence
Make sure “Play/Rec” > “MIDI” MIDI is the linear Song Recorder.
Set the Time Signature, Tempo...
the Time Signature must be set prior to recording...

Some considerations here for the music...
you will ultimately be playing along with a pre-recorded violin track... therefore, you may want to leave a measure or two blank at the top, so that you can place a count-in for yourself when playing the piano part (later). We’ll leave those considerations for you to ponder.

Record the violin portion of the composition.
Play it back — ensure you have it as you like.
You can tap the Song title box and Rename it from the default name to the title of the composition
The data you create in this Song will automatically appear in your UTILITY > “Contents” > “Data Utility” > Song Folder as a .mid File.

Return to the Performance HOME screen.
Now you will “merge” an acoustic piano to this Performance.
On the first available Part tap the “+” icon to add a new instrument.
The “Performance Merge” screen will appear...
Select your piano Performance. It will be added to the violin.

Return to the HOME screen
Deactivate the KBD CTRL icon on the violin Part(s) and leave KBD CTRL active on the piano Part(s).
Press [HOME]
In this condition you can play the piano without triggering the violin. The violin will respond to the sequencer, but is not under Keyboard Control (thus the name of the function) in order to trigger the violin again you would need to either *select* it directly or reactivate the KBD CTRL icons.
Touch “Play/Rec” to return to violin sequence
The sequence will playback the violin, while you will play the piano.

If this is working out... you will want to press [STORE] and then Name and Store this as a New Performance to your User Bank.
Once in your User Bank you will want to link this Song sequence with this Performance so that when the Song is recalled automatically the correct instruments will automatically be recalled.

Extra Credit:
The skills needed to accomplish your goal involve:
__ “Performance Merge” — adding a violin and piano to the same Performance. Normally, the instruments “merged” are played simultaneously in some kind of Layer or Split. In your instance, the violin will played by the Sequencer, while your Keyboard will Control the acoustic piano, live. So you will need to learn to use the KBD CTRL function.

__ “Performance Recorder” MIDI Song operation.

To Bad Mister. Thank you! I'm a bit lost but I'll follow this to the letter.

Some notes.

1. When I merged the piano performance with my Violin performance using BOSS piano with six parts I have to turn on Arp in order to hear the piano. This was a quick fix.

2. I don't seem to 'trigger' the violin to start on a key press but I don't need that really.

3. The Pleyel piece Duo 1 is pretty simple... but.. is there a way to edit mistakes?

4. When I stored this .mid file, I think it saved it to my thumbdrive. Is that were it was supposed to save it?

1. When I merged the piano performance with my Violin performance using BOSS piano with six parts I have to turn on Arp in order to hear the piano. This was a quick fix.

Sorry I don’t understand this can you explain a bit better.
What violin?
What BOSS piano?

4. When I stored this .mid file, I think it saved it to my thumbdrive. Is that were it was supposed to save it?

if you wish. I just stated that whatever you record to the Sequencer is automatically stored internally
Press [UTILITY] > “Contents” > “Data Utility” > in the SONG folder.

"BOSS" = "Two Grands" from the Bosendorfer library?

@Tom: it'd be best to be specific with the actual Performance names. And library name if the Performance is not a factory preset.

Jason recommends and rightfully so that I use the performance names. My first post here. I'll get this.

What violin? I chose "Solo 1st Violin AF1" after searching Strings in Bank: All

What BOSS piano? You were correct in questioning this one. There is no 'BOSS' piano as I had somehow created this in a User bank. I must have saved this somehow and actually do not know what performance it was created with (though given the name Jason is correct in guessing Bosendorfer). I don't know this Montage well. Instead I practiced with Imperial Grand Piano in my Favorites bank this morning.

I read up on quantizing in real-time as the Solo 1st Violin AF1 track I put down was not quite on the beat every time (This piece is in cut time) and it seemed to fix most of the timing errors enough so I could practice the piano part. I'm also able to alter the tempo which really helps.

I want to thank Jason and Bad Mister again for your patience and help.

Tom