vibration:
2. (Physics) A limited reciprocating motion of a particle of an elastic body or medium in alternately opposite directions from its position of equilibrium, when that equilibrium has been disturbed, as when a stretched cord or other body produces musical notes, or particles of air transmit sounds to the ear. The path of the particle may be in a straight line, in a circular arc, or in any curve whatever.

oscillation:
2. fluctuation; variation; change back and forth.

period:
1. A portion of time as limited and determined by some recurring phenomenon
2. hence: A stated and recurring interval of time; more generally, an interval of time specified or left indefinite;

interval:
3. A brief space of time between the recurrence of similar conditions or states;
4. (Mus.) Difference in pitch between any two tones.

harmony: in music, the combination of notes (or pitches) that sound simultaneously. The term harmony is used both in the general sense of a succession of simultaneously sounded pitches and for a single instance of pitches sounding together. In this second meaning, the term harmony is synonymous with chord. Harmony stands in contrast to melody (q.v.; pitches sounding one after another); with melody and rhythm (the stresses and durations of sound), it is one of the three primary elements of music.

melody: 2. (Mus.) A rhythmical succession of single tones, ranging for the most part within a given key, and so related together as to form a musical whole, having the unity of what is technically called a musical thought, at once pleasing to the ear and characteristic in expression.

rhythm:
2. (Mus.) Movement in musical time, with periodical recurrence of accent; the measured beat or pulse which marks the character and expression of the music; symmetry of movement and accent. --Moore (Encyc.)