A: Yeah, this one is for the theory geeks, really fundamental. The 10th already gives you the open voicing of the root and 1st inversions of the triad. But now the solid 11th gives you the open voicing for the 2nd inversion of the triad! So you have all three. This allows unbroken scalar counterpoint with left handed open voicings which will kinda be a brand new thing for piano. For example, you can strike a solid 10th followed by a solid 11th for a descending bass line with the 7th in the bass. There’s other idioms, too. My arrangements of America the Beautiful and Blackbird are full of solid 11ths mixed in with seamlessly with the 10ths.
