After 20 years as dean of the College of Music, Daniel P. Sher will step away from the post in June — but he isn’t going quietly. First, student musicians at the college will dedicate their performance of Beethoven’s Ninth Symphony at Boettcher Concert Hall in Denver on May 1 to the outgoing dean. The celebration will continue May 2 with a free, public musical fete by faculty performers at Macky Auditorium, including world premiere performances of “Sher’s Originals,” penned by faculty composers.