Performing a glissando on a clarinet is one of the more advanced techniques that a musician can learn. A glissando is a rapid slide through a series of consecutive notes in a scale. On reed wind instruments like the clarinet, this is particularly tough because the notes must be played without breaks. There are two ways to preform a glissando: the "finger slide" and the "upward lip."
Play the first note of the glissando holding a steady embouchure.
Slide your finger slowly off from the key you are playing while keeping the embouchure steady.
Slide the remaining fingers of from the keys in the same manner until the final note in the glissando is reached.
Begin playing a lower pitch of the first note in the upper register by at least a semitone.
Play the first note while changing the fingering to the next note.
Hold down the pitch of the note by slacking your embouchure so that the note does not rise.
Raise the pitch of the note toward the next by strengthening your embouchure.
Breathe and throat while fingering to the next note. Continue this process until the final note is reached.
Finger slide glissando requires the musician to know the range of the keys on the clarinet. Every instrument is different and has different release points. It may take quite a while to master this technique.
With the upward lip, the aim is to raise the pitch of the note by fingering by playing a note that is flat to the fingering you are using. Then reach the fingering you are aiming for and return your embouchure to normal.