The previous post finished with my dismay at hearing 'Bach is pure mathematics.' It is not. This post is on the opposite; the musical language of the heart.
‘Heart’ is not all sweetness and light—dolce and giocoso. It can be noble and great – nobilimente and grandioso; with force and fire – con forza, con fuoco (not force and confusion, as in some of your author’s work); tearful and sad – lacrimoso and solennemente; happy – festoso; and so on.
Musical intervals affect us. Consider the augmented fourth, also called the tritone and even diabolus in musica: ‘the devil’s interval’. Ominous, unsettling, unresolved. Gustav Holst featured the augmented fourth in Mars from The Planets suite. On hearing Mars, Geezer Butler of Black Sabbath wrote the riff that became the iconic eponymous song Black Sabbath. The ominous terror that Holst conjures with a full orchestra Sabbath achieve with amplification. Stravinsky went one step further with the Petrushka chord—two major triads a tritone apart—nothing less than an act of musical violence.
Consider the major and minor keys and what they can mean: recall—or listen to—the Beatles’ Norwegian Wood: the sun shines until the minor-key of the chorus darkens the sky. Seal’s Kiss from a Rose is another beautiful example of a song changing back and forth from major to minor. Seal handles the listener’s heart through the transitions and chooses to finish with a bare perfect fifth: neither major nor minor. Yet all is resolved.
A minor third melody note within a major harmony can be called ‘blue’ note. George Gershwin was instrumental—pun intended—in bringing this device from African-American blues musicians onto the concert stage; the introductory clarinet solo to Rhapsody in Blue is perhaps the most famous example. The Spanish composer F. Moreno-Torroba loved Gershwin’s music and used this device in, among other works, Torija from the 'Castles of Spain' collection. Torroba has firmly established the listener’s ear in D major—with an f-sharp—yet the first beat of bar four leans on an f-natural. Torija is referenced further below. He makes the point for us that a good writer can write a sad tune in a major key: Torija in D major is subtitled ‘elegy’. His Arada in A major from 'Suite Castellana' is another such piece.
The opposite of a blue note is a major third in a minor key; the ‘Picardy Third’ is such a device. The third degree of the scale was ‘admitted’ into the final chord of a piece music from around 1500, and the Picardy Third is a major third in the final chord of a piece of music in a minor key. It can smile! A pleasant surprise to conclude a piece, as effective today as 500 years ago.
Recall the dominant seventh and suspended fourth (sus4) chords. The seventh chord demands to go somewhere, while the sus4 needs resolving downwards to the third of the chord. When these conventions are broken, we can have the interminably unresolved music of Richard Wagner and the hilarious faux-Beethoven of Dudley Moore’s never ending cadence.
The effects of these notes and intervals are not mere theory: when properly handled they are real, observable and tangible in my own performances and those of others. The composers have written the notes with intent: to mean something. What follows are some of the skills we need to speak their language and say something meaningful.
 Butler never kept the connection secret.
 Stravinsky’s Petrushka was a very bad puppet in his opera by the same name. The chord can also be found in earlier music.
 Steel-string players and singers routinely use micro-tones between the minor and major 3rd degrees of the scale. Other degrees of the scale can be made ‘blue’ also.
 Clark, W. A., Krause, W. C., Federico Moreno Torroba, A Musical Life in Three Acts, Oxford University Press, 2013, p373
 Arada is about an ox that spends all day every day lumbering up and down working a field in Spain. However beautiful the music, the ox is not happy. This is hard work!
 Harvard Dictionary of Music, 2nd ed., W. Apel, p667.
 “Dudley Moore Beethoven Sonata Parody” YouTube, uploaded by Jondinerstein, 4th Jan, 2007 https://www.youtube.com/watch?v=GazlqD4mLvw