How did Mitchell get that sound, clear and precise, yet the size of Grand Central Station? His tone was always big, but after 1966 when he changed his bass tuning from fourths to fifths (as violin, viola and cello are tuned), it became enormous. He explained it to Gene Lees:
If you tune an instrument in fourths, you get a scale that is shorter physically. The top notes are lower, the bottom notes are higher in pitch. If you tune an instrument in fifths, you get a bigger scale. The top notes are higher, the low notes are lower.
There's more to it than that; the tuning in fifths also effects how the notes sustain, or ring. For detail, read the entire interview with Mitchell in Lees' indispensable book Cats of Any Color. It is fascinating for the fluidity, profundity and coherence of Mitchell's ideas about music and life.
Mitchell died in 1992. Mays is thriving.