Dave Matthews Watch Me Sketch a Penis!

9/12/2012 8:50 AM PDT BY TMZ STAFF

Like Da Vinci ... or Michelangelo ... Dave Matthews is an artist who appreciates the male form ... and last night, he sketched out an image of a naked man ... right on the street.

Matthews was hangin' at a hotel in Hollywood ... when a man approached him and asked for an autograph. Dave went the extra mile ... and drew the man a picture.

Turns out, Matthews has a habit of churning out sketches for fans -- and his art pieces are pretty valuable ... usually starting around $500 a pop ... and some raked in several thousand dollars.

Check out Matthews in action -- banging out not one, but two sketches ... including a little birdie ... the kind that lives between your ring finger and your pointer.