Piano is great and offers something Bass fiddle does not! Check out recording such as Jin Ju playing Schumann Fantasie in C opus 17 (available on Qobuz) 3rd movement, between 2:20-30 min mark, Steinway 1901 Concert Grand Piano D per the liner notes.
…the Piano can play bass notes quietly (hence the full name of the instrument - piano forte). While these low notes may seem anti-climactic for some, the low register of a good piano has an attack to it, especially when played softly, that is beautiful along with tone and overtones, and decay of the note. A fiddle is generally played loud and consistent in attack, and generally all the low notes all the time (so it’s convenient for use in evaluation as well as what the instrument offers in its own right), whereas piano is playing usually higher notes as well and more often. So you need the right recording. I’m not saying a bass fiddle can’t play notes quietly but the piano is pretty unique in what it does. If a system can produce these notes well, it is challenging. “One note bass” from some drums or techno or pop music is one indicator of bass but misses a lot in sonority and tone.
