I watched all of the "Tracking Day" video. It is typical of any professional studio one would find in Nashville. That it was in a house does not change the fact that it is a professional studio in use by professional musicians.

The process and procedures used reflect the way someone with a rough demo could get a good demo and perhaps even a radio-ready demo out of a professional studio at a reasonable cost. Without a vocal by the client or a vocalist used in the studio, the final track would be of limited use unless it was an instrumental.

As was stated, someone listened to the client demo and transcribed it to the extent that there was something to transcribe. That transcription was done in Nashville Number System. It just as well could have been done in standard notation. It is possible that none of those guys could read standard notation. Who knows, but I doubt it.
They looked to be pretty seasoned pros.

A lot of basic demos get made this way along with a few radio-ready songs.

How any of this relates to BIAB through the use of the Nashville Number System is a bit of a mystery to me. Obviously, BIAB can understand very basic numeric symbolic input.

These guys are listening to each other and modifying their playing based on what they hear and then having conversations to further modify the song all in real-time. This is standard recording studio stuff.

You don't have to go to Juilliard to write a song but you can not use NNS without some understanding of music. !,4,5...the 5 of what?

Obviously, most people who buy BIAB have some idea of what it does and will look at the videos that PG Music has made and learn to use the product. Many produce some very good music as can be listened to here on the forum. The studio will never do what BIAB does and BIAB will never do what a studio of the type in the video does. Well...who knows what AI software will do in the future but for the present, I will stick by my statement.

So...just as an experiment, go input the number symbols from the post I made into BIAB and assume it was written only for piano. As BIAB, and your keyboard for that matter does not have the small zero/degree-looking symbol for a diminished chord how will you get the #1dim chord in. How would you even know what that symbol meant or what a sharp diminished chord is? Without some reference, a 1,4,5, and C, F, G are equally meaningless.

Billy

“Amazing! I’ll be working with Jaco Pastorius, Charlie Parker, Art Tatum, and Buddy Rich, and you’re telling me it’s not that great of a gig?
“Well…” Saint Peter, hesitated, “God’s got this girlfriend who thinks she can sing…”