Remarkably, this album is about the only recorded document of the mid-'80s-to-mid-'90s version of the Tony Rice Unit. Led by the most influential bluegrass-based guitarist ever, that lineup -- Rice, brother Wyatt on second guitar, mandolinist Jimmy Gaudreau, and brothers Ronnie (bass) and Rickie (fiddle) Simpkins -- had torn up audiences for years with their inspired performances before scattering when Rice suffered some personal setbacks, most notably the loss of his voice. The group was caught in its instrumental prime here, and on an assortment of material that demonstrates the breadth of the players' interests. Aside from a characteristically nuanced solo guitar arrangement of "Danny Boy" and a blistering live recording of "Sally Goodin", the cuts come from late 1996 sessions and range from several Bill Monroe numbers ("Gold Rush" and "Jerusalem Ridge") through a slinky Rice original, "Manzanita (1st Variation)" to Django Reinhardt's "Swing 42". As on the Unit's first recording more than 20 years ago, Manzanita, what binds these explorations is a running thread of crisp bluegrass timing and rhythms, creating a musical context that is never hidden for too long. There's no exact analogue to be-bop in bluegrass, but the interplay of melody and variation here is about as close to it as you can get. There have been recent reports of Rice essaying a few harmony vocals at recent appearances, but even if he returns completely, it's unlikely this particular lineup will be heard at more than the occasional reunion. That makes Unit Of Measure a slightly bittersweet, but perhaps even more moving, collection.