Nach:  After (as "in the manner of"); behind.

Nachtmusik:  "Night music." A serenade.

Natural:  A musical symbol which cancels a previous sharp or flat.

Neumatic:  One style of chant in which two to four pitches occur on one syllable; in contrast to melismatic and syllabic.

Non:  No; not.

Non troppo:  Not too much. Used with other terms, e.g. non troppo allegro, not too fast.

Nonharmonic tones:  A designation for tones outside the harmonic structure of the chord. Two frequently used examples are the passing tone and the appoggiatura.

Notation:  A term for a system of expressing musical sounds through the use of written characters, called notes.

Nuance:  Subtle variations in tempo, phrasing, dynamics, etc., to enhance a musical performance.

Octave:  The eighth tone above a given pitch, with twice as many vibrations per second, or below a given pitch, with half as many vibrations.

Octet:  A piece for eight instruments or voices.

Open fifth:  A triad without a third.

Open strings:  Strings are not stopped, fingured, or fretted.

Orchestra:  A large group of musicians made up of string, brass, woodwind, and percussion instruments.

Orchestration:  The art of writing, arranging, or scoring for the orchestra.

Ornamentation:  Note or notes added to the original melodic line for embellishment and added interest.

Ornaments:  Melodic embellishments, either written or improvised.

Ossia:  "Or." Indicating an alternative passage or version.

Ostinato:  A repeated melodic or rhythmic pattern, frequently appearing in the bass line.

Ottava:  Octave.

Ottava alta:  (8va) An octave higher.

Ottave bassa:  (8va or 8vb) An octave lower.

Overtones:  The almost inaudible higher tones which occur with the fundamental tone. They are the result of the vibration of small sections of a string (instrument) or a column of air. Other general terms for overtones are partials and harmonics.