Waterville music teacher Dan Keller performs with his high school students Tuesday night after he was surprised with the Maine Music Educators Association’s Hall of Fame award. The award, presented during the school department’s spring orchestra concert, was recognition for Keller’s decades of  contributions to music education. Keller began teaching music in Waterville public schools in 1981 and started a high school orchestra there in 1986, according to the association. The stringed-instrument program currently has about 200 students in grades 4 through 12, it said. Keller is also chairman of the high school’s visual and performing arts department.