This video describes the function of the three modes of the LINK button.
TRACK 1, HALF and IND.
Track 1 is activated by default.
Track 1 means every track will play the same scale and change pattern at the same time as Track 1.
TRACK 1 mirrors the way a band of musicians usually play, in which all of the instruments change chord at the same time, and only play notes in the chord they are currently on.
HALF means all tracks change pattern together. However any track that is half linked can be in a different scale. An example of this is in Jazz music, where the musicians change chords together but some of the notes can be from 'out of key'.
INDEPENDANT mode means that both the pattern changes and the scale are completely INDEPENDANT of other tracks. A common way to use this feature would be to have a bass-line that does not change while other tracks change around it.