He learned how to play the 'ukulele in fourth grade, but his interest in kī hō‘alu, or Hawaiian slack key guitar, was sparked in high school when he heard Keola Beamer on the radio.
In 1975, Kotani enrolled in Peter Medeiros' slack key guitar class at the University of Hawaii Continuing Education program.
Kotani returned to the University of Hawai'i program in 1986 to teach and pass on his knowledge of the Hawaiian slack key style to others.
Kotani followed up his debut with Kani Kī hō‘alu in 1995, To Honor a Queen: The Music of Lili'uokalani in 2002, Paka Ua (Raindrops) in 2005, and Hō'ihi (Respect) in 2008.
He followed up in 2007 with an instructional DVD titled Guitar Playing Hawaiian Style with Ozzie Kotani: Kī Hō‘alu Vol.