Mickey Hart -- a longtime drummer for the "Grateful Dead" -- says he has NO IDEA why a warrant has been issued for his arrest ... telling TMZ the assault allegations against him are completely bogus.
We broke the story ... Hart has been accused of beating up a person at a Mickey Hart Band concert in Kentucky on Sept. 8.
Now, Hart is lashing back ... telling TMZ, "I am totally baffled by a bizarre claim of assault by me coming out of Kentucky -- the home of Bluegrass and a state I love dearly."
He adds, "Any accusation or claim of assault against me is completely false and without any basis whatsoever. I played drums on 'Shakedown Street,' but I never expected to be 'The Victim or the Crime.'"
Officials have not revealed the identity of Hart's accuser -- and so far, the details surrounding the alleged attack are unclear.