What are "intervals" in music?

Intervals in music refer specifically to the distance between two pitches. This distance is measured in terms of both the number of steps and the specific relationship between the pitches. For example, an interval can be described as a second (two adjacent notes), a third (three notes apart), or a fifth (five notes apart), among many others. Intervals are fundamental to music theory, as they form the basis for scales, chords, and harmonies. Understanding intervals is crucial for musicians as it helps them with tuning, harmonization, and the overall structure of musical compositions.

The other options relate to different musical concepts. Tempo variations pertain to the speed of the music, dynamics involve the loudness or softness of a performance, and the number of instruments playing together refers to instrumentation rather than pitch relationships. Each of these areas is important in music, but they do not define what intervals are.