Although Bush has played straight-ahead bluegrass on mandolin, fiddle and guitar on countless occasions, he does stress that there's a difference between that style and the music he creates.
"I take pride in considering myself a bluegrass musician," he said. "But I wouldn't want to mislead anyone that it's what I go around playing. What I play with our quartet is - I don't know - contemporary music played with acoustic instruments, I guess."
It travels even beyond the progressions Bush helped forge with New Grass Revival from 1972 to 1989.
"We took what we got from people that were already making progressive bluegrass, and then we kind of did improvisational, rock-influenced things with our bluegrass instruments," said Bush, who also grew up listening to The Beatles. "When Rubber Soul came out, and I heard 'I've Just Seen A Face,' that sounded like bluegrass to me.
"What I see happening now is that you have these young so-called jam bands playing bluegrass instruments," Bush observed. "Those bands are young and playing for a young audience just like New Grass Revival did. It is interesting to me that there is a young audience that wants to find out about acoustic sounds. They're having fun digging these young bands that are also discovering the same joy that we discovered in the early '70s."
The variety of flavors that Bush infuses into his music serves him well, notes his agent, David Lloyd of the International Music Network agency.
"He crosses over between a lot of venues and audiences. We've broken him into performing arts centers. He plays bluegrass festivals, obviously. And he's a big force in the jam band scene," said Lloyd.
Lloyd also admires his client's "incredible amount of energy on stage and off. He's inspiring."
Bush is confident that bluegrass and the acoustic music that goes beyond it will continue to be enjoyed by new audiences. He is happy to see a strong bluegrass presence in Nashville, and not just in its own genre.
"When you can hear Stuart Duncan or Aubrey Haynie playing fiddle on Country records, that's a healthy thing," said Bush.
As for the king of his own world, Bush said, "I'm still enjoying getting out and playing. Somebody asked me, 'what's your goal?' I said to be able to continue to improve as a player and singer. And I feel like I have a lot of room for improvement. And that's my goal.
"I'm still thinking about the next thing I'm going to do, which is good," Bush said. "I feel fortunate that I've gotten to play with a lot of my musical heroes. And I've been fortunate to be in the audience to hear a lot of great notes played by other people." By Rob Patterson