Rhythm Combo usually means
guitar, keyboard, double-bass (or bass electric guitar), and drums. It is
the basic minimum combination for jazz,
band and popular music
groups. When part of a larger group such as a Big Band, it is called the
A rhythm combo will often accompany a singer, or a solo instrumental player
such as a trumpeter or saxophonist. If you add a clarinet, trumpet and trombone
you get a Traditional Jazz band.
If you add a lead guitar and a singer you get a rock group.