Arpeggio, glissando, and portamento: signs and performance on instruments

Definition

Arpeggio: the notes of a chord played one after another, usually from bottom to top, instead of simultaneously. As an ornament it is indicated by a vertical wavy line in front of the chord.
Glissando (abbreviated gliss.): passing from one note to another by “sliding” through all the intermediate pitches, written with a straight or wavy line between the two notes.
Portamento: a short, expressive slide from one note to another, typical of voice and strings, which does not aim to let the intermediate notes be heard but only to connect.

A continuous wavy line crossing two staves indicates a single arpeggio from bottom to top with both hands; two separate lines indicate two simultaneous arpeggios.
A downward arrow at the end of the line asks for the arpeggio from top to bottom.
The speed depends on the character: extremely fast like an acciaccatura in a forte, slow and “harp-like” in a lyrical piece.
It should not be confused with the written-out arpeggio (broken-note accompaniment, such as the Alberti bass), which is a type of figuration.

Instrument	How it is achieved	Practical notes
Piano	sliding fingernails or fingertips across the white or black keys	only white-key (diatonic) or black-key (pentatonic) scales are possible
Harp	dragging the fingers across the strings	the pedals choose the notes: scales, seventh chords, or whole-tone scales can be obtained
Strings	finger sliding along the string	continuous; also possible on harmonics
Trombone	slide movement	continuous, but only within a tritone between first and seventh position
Pedal timpani	changing the pedal while the head vibrates	“howling” effect
Voice, theremin, synth	continuous	the portamento of monophonic synths is set with the glide time
Winds	with lips and keys (clarinet, trumpet)	often mixed: a fast scale fused into a single gesture

Always write the starting note and the arrival note with their rhythm: the glissando occupies the time of the first note.
For the harp, indicate the pedal setting before the glissando; for the piano, specify white or black keys if the arrival note does not make it clear.
In string writing, port. or a thin line indicates expressive portamento; gliss. indicates a more obvious effect.
In the DAW, a continuous glissando is obtained with pitch bend (setting the right range) or with the synth's glide; a “stepped” one (piano, harp) must be programmed note by note.

Gershwin, Rhapsody in Blue: the clarinet opening is a low trill followed by a very long ascending glissando.
Stravinsky, The Firebird, introduction: harmonic glissandi in the strings, a spectral sound.
Bartók, Music for Strings, Percussion and Celesta: pedal timpani glissandi.
Bartók, Concerto for Orchestra, fourth movement: trombone glissandi in a mocking tone.
Ravel and Debussy: harp glissandi like brushstrokes of color.
In G-funk and West Coast hip hop synth leads, the portamento between notes is a distinctive stylistic element.

The arpeggio as an ornament softens a chord in a slow piece and makes it “cascading”.
An upward harp or string glissando is an excellent acoustic riser before a climax.
The glissando of trombones and timpani brings irony or menace; that of strings in harmonics, mystery.
In production, the glide of 808 basses is the portamento of the 21st century: calibrate it carefully to the tempo of the track.

Write a C major chord on two staves with a single arpeggio and then with separate arpeggios.
Set the harp pedals for a glissando on the diminished seventh chord B–D–F–Ab.
Program in the DAW a one-octave string glissando in one bar, then a piano one on the white keys.

Ornaments; Harp: pedals, range, and writing; Brass: ranges and registers; String techniques; Piano accompaniment patterns; Writing 808 lines.