His vocal range was very wide. He could sing effortlessly on the upper range of the Tenor ladder. But more amazing was the fact that he could make acrobatics and coloraturas on those very high notes.
Chazan William Goldberg who was the Secretary of the “Chazonim Farband” (The Orthodox Chazonim Association) had a typical way of saying it. He expressed it in Yiddish this way: “ Er lehgt zich dort shlofen” ! Meaning: "He is laying down there (on those high notes) to sleep" ! .
Moishe Koussevitzky could start a Shabbos Service at eight in the morning and finish it at two in the afternoon, all the time shooting with top C’s and top D’s without ever tiering or straining his voice.
People use to love those high notes and always begged for more and Moishe very obligingly accommodated them. Moishe was a hard worker. He used to train for hours a day vocalizing and singing.
I have a cousin in Montreal Canada by the name of Willy Frankel. When Moishe Koussevitzky used to come to Montreal for concerts, he was staying at his house where he had a very beautiful basement apartment all for himself. Willy told me, that Moishe was practicing for eight hours every day without interruption.
Moishe not only possessed a tremendous technique, but his voice was very flexible, his coloratura clear and rolling and he created key phrases in Chazonus which all young Chazonim are trying to emulate.
There is one problem as a result of this, that many of them are making a show out of the prayers. This could be the reason why nowadays people are not attracted as much anymore to listen to Chazonim as they were during the Golden Era of Josseleh and Kwartin. When going to Shul (Synagogue), people want to pray and feel lifted up by the prayers. For a show, they go to the theater
One of the most famous pieces for which Moishe Koussevitzky is remembered, is the prayer “Sheyiboneh Beis Hamikdosh” recited at the end of each service. This composition was composed by the late Chazan Israel Shorr and was made popular by Moishe Koussevitzky.