Many a jazz combo is a term used to describe a TRIO, which is a group of three musicians. A jazz TRIO typically consists of a piano, bass, and drums, but can also include other instruments such as guitar, saxophone, or trumpet. Trios are popular in jazz music because they allow for more improvisation and interaction between the musicians. The term 'many a jazz combo' is often used to refer to any jazz TRIO, regardless of the instruments used.