The cello is the lowest-pitched member of the standard string quartet.
A traditional string quartet contains two violins, one viola, and one cello. The cello supplies the ensemble's lowest regular part while also carrying lyrical melodies in a register that can resemble the human voice. Players usually sit with the instrument held between the knees, its endpin resting on the floor, and bow the four strings with a horsehair bow.
The cello's four strings are commonly tuned in fifths to C2, G2, D3, and A3. It uses a combination of bass and treble clefs, with tenor clef helping avoid excessive ledger lines in its upper register. Its body is much larger than a violin or viola but small enough for a seated performer to control.
The double bass can play lower notes, but it is not part of the standard string quartet. That is why “lowest-pitched member of the quartet” means cello rather than double bass. Cellos are also important in orchestras, chamber music, solo repertoire, and modern popular recordings.