Oboe | A woodwind instrument with a slender, tubular body, played with a double-reed mouthpiece.
Octave | (Abbreviation: 8va or P8) The interval between two notes of the same name. Also the name of each of these two notes. The name comes from the Latin word for eight, referring to the eight diatonic degrees within the interval. (Also perfect octave.)
Ode | A lyric poem tha addresses (and often praises) a particular subject.
Offbeat | Any of the normally unaccented beats in a bar.
Open chord | On a stringed instrument, a chord that includes notes played with open, or ‘unstopped,’ strings.
Open note | A note played on an open string of a string instrument. Also the notes on a wind instrument that do not make use of valves or stopping.
Open string | On a stringed instrument, an unstopped string that is allowed to vibrate along its whole length.
Open tuning | On a guitar, a tuning that gives the sound of a chord when the intrument is strummed without fretting (that is, without pressing any of the strings).
Opera | A type of music performance that is generally sung throughout, combining vocal and instrumental music with poetry and drama, acting and pantomime, scenery, and costumes. Also the plural form of the word ‘opus.’
Operetta | A light, entertaining version of Romantic opera with spoken dialogue between numbers.
Opus | (Abbreviation: Op.) A separate composition or set of compositions by a particular composer, usually ordered by date of publication (example: Opus 28).
Oratorio | A large musical work for orchestra and voices, based on religious or serious texts; similar to an opera, but performed without the use of scenery, costumes, or action.
Orchestral bells | (See glockenspiel.)
Orchestration | The process of arranging a piece of music for an orchestra. Also the process of composing the music for a movie or play. (Also scoring.)
Organ | A large musical instrument with rows of tuned pipes that are sounded by compressed air and played using one or more keyboards (including a foot-operated pedal keyboard) to produce a wide range of musical effects. (Also pipe organ.) Also a smaller instrument without pipes that produces similar sounds.
Ornamentation | (See embellishment.)
Ossia | A general term that means ‘or.’
Ottava alta | A general term that means ‘play or sing an octave higher.’ (Also all’ 8va alta.)
Outro | (See coda.)
Overblowing | A technique used in playing a wind instrument to produce a different pitch by changing the direction and/or force of the air stream.
Overtone | (See harmonic.)
Overture | An extended orchestral introduction to a larger work, such as an opera, oratorio, or suite.