A glissando (plural: glissandi , abbreviated gliss. ) is a glide from one pitch to another. It is an Italianized musical term derived from the French glisser , to glide, It is also where the pianist slides across the piano with his or her fingernails .

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Glissando vs. portamento

Prescriptive attempts ^[1] to distinguish the glissando from the portamento by limiting the former to the filling in of discrete intermediate pitches on instruments like the piano, harp and fretted strings have run up against established usage ^[2] of instruments like the trombone and timpani. The latter could thus be thought of as capable of either 'glissando' or 'portamento', depending on whether the drum was rolled or not. The clarinet gesture that opens Rhapsody in Blue could likewise be thought of either way, being originally for piano, but is in practice played as a portamento and described as a glissando. In cases where the destination and goal pitches are reduced to starting and stopping points as in James Tenney's Cellogram, or points of inflection, as in the sirens of Varèse's Hyperprism, the term portamento (conjuring a decorative effect) seems hardly adequate for what is a sonorous object in its own right and these are called glissando.

'Discrete glissando'

On some instruments (e.g., piano, harp, xylophone), discrete tones are clearly audible when sliding. For example, on a keyboard, the player can slide his or her fingertips across the white keys or their fingers over the black keys, producing either a C major scale or an F# major pentatonic (or their relative modes); or, by performing both at once, it is possible to produce a full chromatic scale, but this is difficult. On a harp, the player can slide his/her finger across the strings, quickly playing the scale (or on pedal harp even arpeggios such as C flat-D-E sharp-F-G sharp-A flat-B). Wind, brass and fretted stringed instrument players can effect an extremely rapid chromatic scale (ex: sliding up or down a string quickly on a fretted instrument), going through an infinite number of pitches. Arpeggio effects (likewise named glissando) are also obtained on the harmonic series by bowed strings and brass, especially the french horn.

'Continuous glissando' or portamento

Musical instruments with continuously variable pitch can effect a portamento over a substantial range. These include unfretted stringed instruments (such as the violin, viola, cello and double bass and fretless guitars), stringed instruments with a way of stretching the strings (such as the guitar or sitar), a fretted guitar or lap steel guitar when accompanied with the use of a slide, wind instruments without valves or stops (such as the trombone or slide whistle), timpani (kettledrums), electronic instruments (such as the theremin, the ondes martenot, synthesizers and keytars), the water organ, and the human voice. The musical saw, or "singing saw", plays entirely in a glissando .

Portamenti can be produced over a limited range on most instruments; for example, fretted stringed instruments (such as the guitar or mandolin) can effect a portamento by pushing the string across the fingerboard. This is commonly called note bending rather than a portamento.

Brass and wind instruments such as the flute or trumpet can effect a similarly limited slide by altering the breath pressure, while the clarinet can achieve this by slowly dragging fingers off tone holes while adjusting the embouchure. The trombone is especially conducive to producing portamenti of up to an augmented fourth, though the effect is limited by the slide position and partial of both notes involved.

Tunable percussion instruments such as the drum or conga can effect this by applying or releasing pressure on the head while striking.

Many electric guitars are fitted with a tremolo arm which can produce either a portamento or a vibrato or a combination of both (but not a true tremolo despite the name). By pressing the arm towards the body of the guitar, the guitarist moves the bridge of the guitar both away from the body and forward (towards the headstock), thereby decreasing string tension and lowering the pitch any notes that are sounding. This technique can often produce portamenti of incredible range, with the guitarist often being able to reduce tension to the point that the strings become slack. Such a portamento however is rarely used to melodic effect, instead being implemented as a special effect; however, some guitarists (most notably Jimi Hendrix) have strongly focused on the use of extended portamenti for melodic effect. Some guitars feature a vibrato that is also capable of being pulled away from the guitar body, resulting in an increase in string tension and therefore an increase in pitch. Extended use of portamenti figures on guitars without locking nuts can cause the strings to be pulled out of tune.

Portamento can often be generated automatically on synthesizers, where a parameter setting can be used to control the speed at which an oscillator moves to a new pitch. Often this parameter is called glide. Alternatively, portamento effects can be produced manually by a skilled player through the use of the pitch bend wheel at the side of many synthesizer keyboards, or alternatively by means of a ribbon controller. Synth lines with lots of portamento defined West Coast G funk of the mid 1990s, and continue to be a distinctive part of electronic music today, as well as progressive rock music (see Dream Theater's Jordan Rudess.)

In MIDI sequencing, portamento can be generated by using a channel message that creates a sliding effect by smoothly changing pitch from the last note played to the pitch of the currently playing note.

The Casio CZ-101 was one of the first synthesizers to have a polyphonic portamento effect.

References

1. Harvard Dictionary of Music
2. ibid.