Interval root thumb|center|400px|Intervals in the harmonic series Although intervals are usually designated in relation to their lower note, David Cope and HindemithHindemith, Paul (1934). The Craft of Musical Composition. New York: Associated Music Publishers. Cited in Cope (1997), p. 40–41. both suggest the concept of interval root. To determine an interval's root, one locates its nearest approximation in the harmonic series. The root of a perfect fourth, then, is its top note because it is an octave of the fundamental in the hypothetical harmonic series. The bottom note of every odd diatonically numbered intervals are the roots, as are the tops of all even numbered intervals. The root of a collection of intervals or a chord is thus determined by the interval root of its strongest interval.
interval root thumb|center|400px|intervals in the harmonic series although intervals are usually designated in relation to their lower note david cope and hindemithhindemith paul (1934) the craft of musical composition new york associated music publishers cited in cope (1997) p 40–41 both suggest the concept of interval root to determine an interval's root one locates its nearest approximation in the harmonic series the root of a perfect fourth then is its top note because it is an octave of the fundamental in the hypothetical harmonic series the bottom note of every odd diatonically numbered intervals are the roots as are the tops of all even numbered intervals the root of a collection of intervals or a chord is thus determined by the interval root of its strongest interval