The word ‘Glissando’ comes from a French verb ‘to slide’ and applies to any passage where one note slides rapidly up or down to another. On the piano this is done by drawing the finger quickly up or down the keys and the technique is often used in music written for harp, trombone or any of the string family.
On a stringed instrument, this glissando effect can be achieved by simply sliding from one note to another on the same finger on the same string – it can be used to give a slightly ‘folky’ feel (swooping up to a note as in bluegrass or Celtic fiddle music) or could be used more slowly to add tension or suspense to an arrangement. A common use of glissando is in horror films or psychological dramas when anticipation of something sinister is being built up. One well known pop song which utilised glissando effectively in the string section was ‘Day in the Life’ by the Beatles and it features quite widely in quite a few tracks by ELO.
Although Portamento seems quite similar to glissando in the fact that it’s a gliding from one note to another, it is different in the fact that it doesn’t tend to connect the two notes with the slide but is more of a gentle sliding at one end of the interval or the other. For example, a session violinist could go from say, a D to the same note an octave higher, with the portamento providing a shorter slide at the beginning of the interval, before landing accurately on the higher D – or it could leave the first note, then land a little bit early and swoop up to the upper D. This gives an expressive slide but without the two notes being completely connected. In its’ best use, writing in portamento can add real character and feeling to a phrase, making it full of character and adding interest / life to the strings.
Including both glissando and portamento in a string arrangement can work well for solo instrumentation or a full string section, adding either one skilfully can liven up strings and add excitement or expression.