Hi Tom! It is sort of a play on words through analogy. The words "high note" refer to a successful point or event. For example, "Roger Federer will probably retire if he wins another Grand Slam title to end his career on a high note." Most likely, it was borrowed from music, particularly singing, where it is a physical challenge to reach ("hit") the highest note. Anyway, in your example, the author is simply saying that he/she didn't get along so well with the other party--they were not "singing" happily" or sweetly. If the last meeting was a bad one, he could also write that it had ended on a "sour note." I hope that this helps you. J.