Musical instruments with continuously variable pitch can effect a true glissando over a substantial range. These include unfretted stringed instruments (such as the violin and some bass guitars), stringed instruments with a way of stretching the strings (such as a guitar with a whammy bar), wind instruments without valves or stops (such as the trombone or slide whistle), synthesizers, the human voice, and the water organ.
True glissandi can be produced to at least a limited extent on most instruments; for example, fretted stringed instruments (such as the guitar or mandolin) can effect a glissando of up to a minor third (three semitones) by pushing the string across the fingerboard. Brass and wind instruments such as the flute or trumpet can effect a similarly limited glissando by altering the breath pressure. Tunable percussion instruments such as the drum or conga can effect small glissandi by applying or releasing pressure on the head while striking.
On some instruments, a bending of the tone or continuous sliding is not possible (e.g., piano, harp) As a substitute, the player can play a number of adjacent notes in rapid succession, so that the audible result somewhat resembles a true glissando. For example, on a piano, the player can slide his thumbnail across the white or black keys, producing either a C major scale or a C# major pentatonic (or their relative natural minor scales). On a harp, the player can slide his finger up or down the strings, quickly playing the separate notes. Wind, brass and fretted stringed instrument players can effect an extremely rapid chromatic scale, giving the same effect. These latter techniques are commonly referred to as glissandi in scores and sheet music, although technically they are only "effective" glissandi.
See also: musical terminology