Glissando
Gliding through the tonal space between two notes.
What it means
The glissando, from Italian “glissare” for “to glide,” is the gliding through the tonal space between two notes. It arises when all the notes in between are touched in quick succession without appearing separately articulated. It is notated with a line between the two notes, often with the addition “gliss.”
Musical use
On instruments with a continuous pitch range, such as the trombone, violin, or singing voice, the glissando can be truly continuous. On keyboard instruments it is produced by sweeping over the keys, whereby the semitone or whole-tone steps stay individually audible, and on the harp over the strings. Famous is the clarinet glissando at the start of George Gershwin's Rhapsody in Blue (1924).
The glissando should be distinguished from the portamento, the expressive carrying from one note to another in singing or on strings, which is more a means of expression than an effect, and from the scale, in which each note is articulated singly. It also differs from the arpeggio, in which chord tones sound one after another.
Performance practice
In a glissando, plan the start and target notes exactly, since both should be clearly audible. On string instruments glide with even finger pressure and bow stroke; on the piano sweep with the fingernail or thumb over the keys and keep the hand relaxed.