Settle into music’s home base – the key of C – with “upon one note” and the critically-acclaimed Chameleon Arts Ensemble of Boston. Composed in the final weeks of his life, even as he struggled with terrible illness, Schubert’s C Major Cello Quintet ranks among music’s finest achievements, a work of profound beauty, fragility, and humanity. Haydn’s Piano Trio, Hob. XV:27 and Poulenc’s Sextet for piano and winds are graceful, glittering classics in music’s home key. Rounding out the program, Oliver Knussen invites us into his dream of C with his Fantasia after Purcell for clarinet, violin, cello, and piano.