Yamaha Bb Allegro Clarinet YCL550 ALOffering many features of more advanced professional models, the Yamaha Allegro line of brass and woodwinds is the next logical step in a student's musical progression. When it's time to step it up, it's time for Allegro?. Every day, your student is growing. Like clothes that become too small, eventually a beginning student model horn will start to hold them back. Yamaha offers the perfect line of instruments to keep pace with their burgeoning musical