Teaching intervals to music students is on of those concepts that can easily be either overlooked, or if taught make students wonder why. Like most concepts in music theory, if intervals are just taught but never applied or made practical, there really is very little to recommend teaching them. On the other hand, teaching students what intervals are, how recognize them, and how to use them to improve their sight singing and music reading is an important part of building musicianship in music.
Before going further, I should define what is meant by intervals. In music, an interval is a numeric value that represents the diatonic distance between two pitches. To determine the interval, one counts the first note as 1, and then counts up in increments of 1 for each possible diatonic pitch up to and including the second pitch. For example, from do to mi is a third, because do is counted as one, re is counted as two, and mi is counted as three. Do to sol is a fifth, re to ti is a sixth, and so forth. Not all like intervals are the same size, but when audiated and sung, their differences become apparent aurally in the context of a diatonic scale. Labels of major, minor, and diminished can be applied when the differences in sound have become familiar.
One of the best uses of intervals is to sing scales in different intervals. This is excellent ear training. The most common interval for this use is the third, and singing a scale this way is known as singing a scale “in thirds.” A C major scale ascending in thirds would have pitches of do, mi, re, fa, mi, sol, fa, la, sol, ti, la, do, ti, re, do. The descending scale is do, la, ti, sol, la, fa, sol, mi, fa, re, mi, do, re, ti, do. Other intervals are useful as well. Scales in fourths and fifths and seconds are wonderful for developing solfege skills. On instruments as well as on voice, they also promote even tone across leaps and shifting registers.
Intervals are also quite useful in aiding music reading. The tonic and dominant chords in any key within the range of
the five-line staff are always entirely on lines only or spaces only, while the sub dominant will be on the opposite. This helps in recognizing the sub dominant chord because it is the chord that is located differently. Students can also be taught to recognize arpeggiated chord inversions using intervals. A chord in second inversion has a fourth between the bass note and the tonic, and a chord in first inversion as a fourth between the third and fifth of the chord. Once students are proficient at audiating intervals, they can more easily read them using rules for specific intervals. Among these is that thirds always are space to space or line to line, fifths always go space to space or line to line with one of the same in between, and fourths have a space and a line between the two notes. Recognizing thirds, fourths and fifths quickly is a great advantage, because our diatonic music is loaded with chord patterns. Seconds are an indication of non-chord tones, and a cue for students to look for the chord notes to correctly audiate the harmony.
Intervals are also an important piece of data that our brains use to identify melodies. Along with rhythm, most people will quickly “name that tune” as soon as the interval combination (as opposed to the sequence of individual pitches), meter and rhythm are known. For example, do fa fa fa with a rhythm of quarter, dotted-eighth sixteenth, quarter is almost universally recognized as “Bridal Chorus” from Lohengrin if it begins on the downbeat in common time, or as “O Tannenbaum” if it begins on the anacrusis in 3/4 time. And although most people could not name the pitches involved, nearly everyone can recognize two unisons and a descending major third as the opening of Beethoven’s fifth symphony. It is also true that often the sound of particular intervals are remembered by a well-known excerpt in which they are found; the fourth sounds like the beginning of the Bridal Chorus, the major third sounds like the beginning of Beethoven’s fifth symphony, and so on. Of course, these are only aids to building audiation skills; eventually students should be able to just audiate intervals without relying on such references.
Teaching intervals in a practical way makes them useful and relevant to students, and places them in the correct context for most students. While being able to identify or “spell” intervals is good, it is of little practical value without putting intervals to use in performance and music reading. For those who analyze scores, there are other applications of intervals, but for most school children, the more relevant and practical approach is best.