From Zappa Wiki Jawaka
Vic Mortenson is name-checked on the cover of "Freak Out!" (1966) under the heading "These People Have Contributed Materially In Many Ways To Make Our Music What It Is. Please Do Not Hold It Against Them". He provided drums on a some of the earliest (Studio Z) recorded collaborations of FZ and Captain Beefheart, heard on The Lost Episodes and Mystery Disc.
Mortenson, under his real name of Mortensen, on recounting his exploits with the Magic Band in the "Grow Fins" CD set booklet (p23):
"Frank Zappa once told me, "Vic, you'll never be a blues player". I asked why. He said "Because you've never drunk Thunderbird wine, warm, out of a glove compartment". So I was just trying to catch up. Blues was an entirely new thing".
Mortensen was called up for active service prior to the recordings made under the group's A&M contract.
FZ's Antelope Valley High School associate, Snouffer, aka Alex St. Clair, put aside his guitar and stood in on drums.