This run from high to low, from The Great Gate of Kiev , the finale of Mussorgsky’s Pictures at an Exhibition , illustrates the artistic problem that the Alexander piano is trying to solve: https://www.youtube.com/watch?v=FzqpNEoL1vs&t=379s At the top, the notes are easily identifiable, but near the end the pitch gets increasingly murky. The damage to the artistic intent by the limitations of the instrumental technol…
Why does a bass guitar not suffer from this poor sound quality?
These lower notes are the "muddy" ones, and since pianos have a tough time cleanly making those notes, then it would also mean that bass guitars would, too. Most 7 string guitars only play about a perfect 4th or a perfect 5th below standard tuning because of this inescapable muddiness, and the other extra strings tune upward into the low range of the guitar instead.
Aside from that, it wouldn't matter anyway as guitar instruments are inherently "loose" in their tuning. They may be perfect at the open string and 12th fret if they are properly set up and intonated, but every note in between will be off by a small amount.
Further, the act of fretting and plucking the instrument changes the tone of the generated note, specifically, where and how you strike the string to generate the note changes the overtones, and where and how hard you depress the string behind the fret causes minute shifts in the pitch of the string, not to mention that even minor bending of the string due to hand anatomy and grip pattern will also cause the pitch to change.
Two players can mechanically play the same piece on the same instrument in the same way down to the microsecond, but no matter how accurate they are, there will be detectable differences in the resulting piece.
A piano doesn't have that. You have your three pedals and how hard you depress the key. Still a lot of control over the sound, but if two different pianists play the same piece on the same piano with the same pedal work and finger strength, the results should be essentially identical.
Therefore, the sound quality of the piano is fixed and set based on its original setup and the string lengths it is given, whereas a guitar player can compensate for low level muddiness by altering the playing pattern, striking closer to the bridge with a plectrum or their nails, whatever they need to do to put some brightness into a low note, whereas the piano player only has the option of striking harder or softer, so in the range where a bass and piano compete, the bass can have much less muddiness than a piano.