Sources
Ryan Shriver
Corry Arnold
Joe Jupille

Corry Arnold: "This show is Jerry sitting in with Bay Area bluegrass band High Country: Butch Waller (mandolin, vocals), David Nelson (guitar, vocals) and Rich Wilbur (bass, vocals). The confusion surrounding this tape was cleared up by a Usenet posting from David Nelson, now buried in my wife's deceased hard drive. Nelson was a sometime member of High Country and Jerry sat in. Since all Matrix shows were taped (hallelujah) this artifact survives. The numbers are such standards that it was easy for naive listeners (including me in the past) to assume that Grisman, Wakefield, Peter Rowan or others were involved, since all bluegrass singers imitate Bill Monroe. According to another posting, the band listed at the Matrix that night was "Weird Herald". For various reasons I think that is a bluegrass joke (there is a well-known bluegrass singer named John Herald, and some other facts). High Country was unlisted, or they actually were Weird Herald. Butch Waller sings and plays a lot like Frank Wakefield so Wakefield is often mistakenly listed as appearing on the tape (I'm sure Waller would be complimented). Butch Waller and High Country still reform every New Years to play the Freight and Salvage in Berkeley. Jerry hasn't shown up yet, but you never know."

JGMF has also posted about this show: