From Monkey Island wiki
Jesse Harlin is an in-house composer for LucasArts. He was responsible for recreating the music of the first two Monkey Island games with real instruments for The Secret of Monkey Island: Special Edition and Monkey Island 2 Special Edition: LeChuck's Revenge.
According to interviews, Harlin's biggest challenge was recreating Michael Land's compositions faithfully which wasn't always possible. Land's MIDIs would sometimes use frequencies and notes which couldn't be played physically on the instruments in question which lead to these being replaced by other instruments or being digitally re-pitched to fit the original melody.