. ♪ >> ricky skaggs walked on stage and said, it's hanging room only.ike bats. [ cheers and applause ] >> reporter: the cave music is so popular pbs now broadcasts it. ♪ bluegrass underground featured ricky skaggs, vince gill and leon russell. ♪ >> reporter: every piece of equipment must be carted into the deep. >> this is an experience you just don't have in life no matter if you are playing or walking around. you don't find yourself 300 feet below the surface of the earth. ♪ >> reporter: a concert hall like no other above or below terra firma. kevin tibbles, nbc news, cumberland caverns, tennessee. >>> that's "nbc nightly news" for this saturday. i'm lester holt reporting from new york. i'll see you tomorrow morning on "today." then right back here tomorrow evening. good night. >> the giants and the dodgers, a rivalry for the ages. the rivalry continues next. the heat

. ♪ >> ricky skaggs walked on stage and said, it's hanging room only.plause ] >> reporter: the cave music is so popular pbs now broadcasts it. ♪ bluegrass underground featured ricky skaggs, vince gill and leon russell. ♪ >> reporter: every piece of equipment must be carted into the deep. >> this is an experience you just don't have in life no matter if you are playing or walking around. you don't find yourself 300 feet below the surface of the earth. ♪ >> reporter: a concert hall like no other above or below terra firma. kevin tibbles, nbc news, cumberland caverns, tennessee. >>> that's "nbc nightly news" for this saturday. i'm lester holt reporting from new york. i'll see you tomorrow morning on "today." then right back here tomorrow evening. then right back here tomorrow evening. good night. -- captions by vitac -- www.vitac.com