- Interval = the distance between any two musical tones
- Melodic interval = when the tones are played one after the other = the smallest unit of melody
- Harmonic interval = when the tones are played simultaneously = the smallest unit of harmony
- Interval quantity = the number of scale tones an interval contains (not affected by the presence of sharps and flats) e.g. third interval
- Interval quality = measurement which counts the number of half steps the interval contains (e.g. C to E and C to Eb both contain three scale tones but different numbers of half steps)
