Dave Matthews and Boyd Tinsley: Let's Kiss It Out, Bro!

Dave Matthews celebrated his band's 25th anniversary by making out .... with violinist Boyd Tinsley.

Actually, Boyd started it, Dave just finished it. The sneak attack kiss went down during DMB's anniversary show in Charlottesville, VA this weekend ... just as they were wrapping up an encore performance.

The 30th anniversary show ... probably won't be in North Carolina.