It all depends on which frets are played during the song. If it ranges from

the first fret to the fourth on then your pinky plays it. If the song ranges

from the second fret to the fifth fret then you play it wiht the ring finger. If

from third to sixth then middle finger and if the song ranges from the fourth

fret to the seventh then play it with the index finger.

Hope that helps

there is no fixed finger for the 4th fret..you can very use any finger that you want..like in the previous post it depends..now if you practicing semi-chromatic or chromatic exercises and doing it from the 1st fret then your pinky should be doing the 4th fret.