In musical life not only one bar in instruments are used, because one bar can produce only one note, but there are such instruments.

An example for a one bar instrument is the triangle, which is made of a metal bar bent in a triangular form.

Similarly, the diapason is made of a single bar bent in a U shape. Chorus conductors use it to sound the fundamental tone. The diapason has the advantage that it produces very few and soft other notes in addition to the fundamental note, so its sound is very clean.