Every Young Israel has to have their own Harmonizer. The Harmonizer is the guy who generally does nothing else. He doesn't lain. He doesn't daven for the amud. He rarely gets an aliyah. He doesn't really have much to do with the shul's day-to-day running.
But boy can he harmonize. Or at least he thinks so. Sometimes he can be good at the harmonies; sometimes he is quite poor. But the key thing is that HE thinks he is good, so he keeps on going.
The parts that he generally portrays his skills are:
1) While the Torah is being taken out and put back (especially Etz Chaim)
2) The Kaddish before Musaf
3) If the Chazan sings Michalkel Chaim
4) If the Chazan used the Carlebach Mimkomcha
5) Lecha Dodi
6) Yedid Nefesh
The harmonizer will generally sit somewhere near the bimah so that he could take his position on the side of the bimah when the time calls for it. If you join him in the harmonies, he may give you a weird look and try to sing higher than you. After all, that's HIS job; not yours. Only one Harmonizer per Young Israel.
One of his key traits is being louder than the rest of the congregants. Often the women sitting upstairs or the youth leaders downstairs or the passerbys outside may comment something along the lines of "wow, that guy is trying to do harmony." His goal is to make sure he is known. For what reason? Your guess is as good as mine.
The Harmonizer may tend to assist the Ba'al K'riyah at the end of each aliyah. This may often hurt the congregants in being yotzei the leining, but that generally does not matter to the Harmonizer (not that I'm bitter). Of course, this may not be the fault of the Harmonizer, but does tend to be.
The Harmonizer in my shul knows that he is not very good at the harmonies, and often invites me (who is also not so great) to join him in the harmonies and together we successfully get drowned out by the rest of the congregants. (We are not so loud.) But we like it that way. Once we figure out what it is we are supposed to be doing, we may try some louder harmonies.