When only one musician is playing and instrument or singing, he or she is performing a solo.
Ravi Shankar, full-length portrait, seated, playing the sitar] / Jatendra Orya(?), London
Interlochen, Michigan. National music camp where 300 or more musicians study symphonic music for eight weeks each summer. Girls practicing on the harp
Is he playing alone or do you think there are other musicians with him?
New York, New York. A trio of musicians from Duke Ellington's orchestra during the early morning broadcast
Solo Duet Trio Quartet