Why not the piano as a reference for bass

It's not limited to square waves.  A sawtooth wave also has an instantaneous rise or fall time, as the case may be.

In the real world of music, a square wave would most sound like a clarinet, a sawtooth wave like a string, with bow spikes, a sine wave like a flute, and a triangular wave "flute-like" though none of these instruments are "pure of wave".

So, what's Joni playing (make and model)?

https://youtu.be/_kyQEa-QUd8

Well Tim, I already related the story of the local Yamaha dealer renting the Kravits Center here in West Palm Beach where the Clavinova was definitely on stage.  So the only part of not in your lifetime that you can cling to is the relative standing of the Kravits Center among the world's better venues.  On that score you can relax.  But there us no question that this instrument is for home use, not for world class performance.  With that said, it would not surprise me if world class performers are using them for practice.  If my local dealer is to be trusted that is a fact.  For me the over riding consideration is that mine sounds exactly like a C7 to my ears and is always in tune.  

Dear Bill, yes, I’ve conducted productions in my career at the Kravis, it is a very nice arts center. I should have been more specific in saying for a concert pianist in recital or concerto. That you won’t see. And trust me, no serious classical pianist uses a Clavinova to practice. I’m sorry the discussion has gotten off its original topic. The difference is that between a very good sampled piano keyboard and a concert grand. Please enjoy yours! Best, Tim