The 15th season of the Alpenglow Chamber Music Festival starts Sunday. New this year, five guest musicians join, including a vocalist.Japanese pianist Rieko Aizawa, a Steinway artist who has been with festival since its inception, and 8-year festival veteran and Grammy-nominated violinist Jesse Mills return as artistic directors for a second year. Both are graduates of the Juilliard School and both play solo and orchestral engagements throughout the United States. "This year we will be introducing a double-bassist and a soprano to our audience for the first time," Aizawa said. "More variety of instrumentation allows us to have a bigger palette of musical colors."For the Sept. 11 concert, the festival presents Schubert's "Trout" quintet, which includes the double bass. "This giant version of the cello ... has a very unique singing voice," Aizawa said. "You'll be able to hear its distinctive warm tone very closely, especially in a duo for cello and bass, written by John Harbison." Principal bassist Zachary Cohen of the Milwaukee Symphony joins for this piece.Bringing in a vocalist was something of a radical decision, but this year soprano Ilana Davidson joins in the Sept. 14 concert for "Shepherd and the Rock" by Schubert and a "an exotic and fun piece" by Villa-Lobos that utilizes his native Brazilian folk melodies and rhythms. "Ilana Davidson has an incredibly pure voice, and she moves the hearts of audiences all over the world," Aizawa said.Chicago Symphony cellist Brant Taylor and violist Masumi Rostad from the Pacifica Quartet also join the 2012 Alpenglow Chamber Music Festival, with clarinetist Igor Begelman returning for the grand finale on Sept. 14, "Quartet for the End of Time" by Olivier Messiaen."I believe we can make Alpenglow into a most special and unique musical place, attracting enthusiastic audiences and musicians from all over," Aizawa said. "Music is one way we can all appreciate the beauty of humanity."The Alpenglow Chamber Music Festival performances consist of two public concerts at Lord of the Mountains Lutheran Church in Dillon and two soires in private homes. See www.alpenglowchambermusic.org for info.