In modern times, the most common clarinet and often referred to as the soprano clarinet when required to distinguish it from other clarinets. However, the clarinet in A, just a semitone lower, is regularly used in orchestral, chamber and solo music and an orchestral clarinettist must own both A and B flat clarinets since the repertoire is divided fairly evenly between the two.

The A and B flat clarinets have nearly the same bore and the same mouthpiece and orchestral clarinettists could use the same mouthpiece (and often the same barrel) in a concert. The A and B flat have nearly identical tonal quality, although the A typically has a slightly warmer sound.

The bottom of the clarinet's written range is defined by the keywork on each instrument, standard keywork schemes allowing a low E on the B flat clarinet.