I’m sure you’ve heard the song Do-Re-Me, which Julie Andrews sings to a group of children in the film The Sound of Music. Just in case you haven’t, take a quick look:
The Tonic Sulfa is a way of describing the intervals in the degrees of a major scale using seven short names: DO, RE, MI, FA, SOL, LA, and TI. It is essentially equivalent to the more formal labelling of tonic, supertonic, mediant, subdominant, dominant, submediant, and leading tone, but much simpler to remember. The tonic sulfa is independent of key but, as an example, in the key of C major, it would constitute the notes C, D, E, F, G, A, B and C.
The song comes over as incredibly simple but, as with most of the famous show tunes, is actually quite sophisticated behind the scenes. As you can see from the score below, each phrase starts with the next higher degree of the scale, starting with middle C.
However, what is really neat is that the song actually leaves the key of C major and embarks on a journey through two other keys before returning conveniently to C major at the end. It does this using a harmonic sequence, starting at bars 9 and 10 with the C and F chords (it’s very common in harmonic sequences for there to be two chords, then second being four steps higher); the same phrase is then repeated one step higher at bars 11 and 12 moving from D7 to arrive at the key of G major; and then one step higher again at bars 13 and 14, moving from E7 to arrive at the key of A minor; it is then relatively simple to return to C major in bar 16.
What makes the key changes obvious is the incidence of accidentals in the score. At bar 11, we see an F#, giving us a clue we are shifting to a G major scale (G, A, B, C, D, E, F#, G), and at bar 13 we see both F# and G#, indicating that we are moving to an A melodic minor scale (A, B, C, D, E, F#, G#, A).
So, this song provides us with two lessons in one: the tonic sulfa and harmonic sequences. Not bad, eh?