Fluidity is essential to bluegrass. Its presence carries the listener through the song like a skilled dance partner, while its absence leaves us stepped on and sore. Mason Porter opens up “Up in the Hills” with Joe D’Amico’s gentle mandolin and builds seamlessly from there. The high harmonies and tight rhythm are all the more impressive in this drumless live recording. You probably wouldn’t have to ask twice for Mason Porter to cover “Box of Rain”, and their love of traditional folk songs is well documented in the Philadelphia area. Nonetheless, their originals bring that traditional sound forward into even groovier, bluesier directions.