A hammer-on always raises the pitch of the note that is being played. As with all slurred notes,
only the first note in the pair is actually played with the right hand. Notes are usually played by fretting at a certain position and then playing a string, but with the hammer-on the
procedure is reversed. First you play the open string, then you hammer down on a fret to produce a second tone. You can also begin with a fretted string, and the hammer down on a higher
fret of the same string with your 2nd, 3rd, or 4th finger.