Gitaar met 1 ander instrument, O
| Naam | Compositie | bezetting | |
| Obrovska | Jana | Suite in old style voor fluit en gitaar | fl-gtr |
| Oehring | Helmut | ICH.STILLE. (aus: Rehnebel/Opfer/Puderfinger) | fl-gtr-CD |
| Olaya | Pedro | Canción voor cello en gitaar | gtr-vc |
| Olive | Vivienne | Fantasy on the folksong, “A poor wayfaring stranger” | vl-gtr |
| Olive | Vivienne | Fantasy on the folksong, “A poor wayfaring stranger” | vc-gtr |
| Olofsson | Kent | Alambic I - for alto guitar and electronics | a.gtr-electr |
| Olofsson | Kent | Alambic II - for guitar and electronics | gtr-electr |
| Olofsson | Kent | Il Liuto d'Orfeo for guitar and tape | gtr-tape |
| Olofsson | Kent | The Emerald Windstrings - for clarinet and guitar | kl-gtr |
| Oosterveld | Ernst | Git3 : for guitar trio, 1988 gitaar met electronica | 3gtr-electr |
| Ortiz-Alvarado | William | A Delicate Fire, contralto and guitar (1986) | voc(a)-gtr |
| Ortiz-Alvarado | William | HY-1-4175, guitar and piano (1987) | gtr-pno |
| Ortiz-Alvarado | William | Música de Fiesta, cuatro and guitar (1992) | cuatro-gtr |
| Ortiz-Alvarado | William | Ricanstructions, flute and guitar (1999) | fl-gtr |
| Ortiz-Alvarado | William | Romance, boy soprano (or soprano) and guitar (1988) | voc(sop)-gtr |
| Ortiz-Alvarado | William | Síntesis, guitar and tape (1979) | gtr-tape |
| Ortiz-Alvarado | William | Songs from the Bilingual, baritone and guitar (2000) | voc(bar)-gtr |
| Oudrid | Cristóbal | La Macarena, para violochelo y guitarra | gtr-vc |
| Ourkouzounov | Atanas | Avant, guitar, | gtr-pno |
| Ourkouzounov | Atanas | Macedonian song | fl-gtr |
| Ourkouzounov | Atanas | Makedonski pesen | fl-gtr |
| Ourkouzounov | Atanas | Scherzo A Dix Cordes, cello, guitar, | gtr-vc |
| Ourkouzounov | Atanas | Sonatina Bulgarica, violin, guitar, | vl-gtr |
| Ourkouzounov | Atanas | Sonatine: Hommage À Theodisii Spassov | fl-gtr |