I think a major purpose of music is emotional communication.
More great insights, thanks. I've often heard that music is a universal form of communication, but as your wording suggests, there are other "purposes" of music, such as inspiration, memory aids, social glue, and so on.
As for music needing to be universal in message, that fits with the general wisdom of art that the best paintings, photographs, films, books, cartoons, etc. are about common universal experiences. Non-lyrical music and certain abstract art seem to contradict this at first because music and certain abstract art styles don't depict anything specific in a visual way, but in an abstract way I believe they still do.
I have a deep hypothesis about this, but as a concrete example, consider the song Korrelan posted: "Lonely Boy" by The Black Keys. I looked up the chord progression for that, and it's: E G A, or more abstractly I bIII IV, which is a very common rock progression, and a very appealing one at that. (
https://tabs.ultimate-guitar.com/tab/the_black_keys/lonely_boy_chords_1120149) Why is it so appealing? There are several reasons, but one reason is that the chords are ascending in an obvious way that most people can hear. Part of my hypothesis is that people unconsciously associate abstract emotional concepts with musical passages that reflect those concepts in an auditory way. In this case the emotional concept will be that of ascent/progress, and in this case the musical cause is that the chords are ascending. Here's some corroboration for that conjecture: Consider the jazz song "Movin' On Out". The chord progression has the same chord relationships as "Lonely Boy", bIII IV I, except with the key chord at the end instead of at the beginning of the cycle, and other slight alterations like a different key, different musical genre, and different instruments. The music has the same positive effect, in my opinion: an appealing, positive, powerful sense of progress...
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Movin' On Out
Steve Graeber - Topic
Published on Oct 22, 2015
...so that lyrics are not even needed to reinforce that effect. Visually you can think of this song as a group of three steps that keeps repeating and therefore keeps ascending, with some sort of visual embellishments tying together or dancing around the steps as you ascend (vines? birds? butterflies?). The instrumental solos are the equivalent musical embellishments. The inspiring song I posted, "Venus Isle" by Eric Johnson, is quite similar, although the second chord is different: bVI instead of bIII, so it slightly alters the ascending effect. Again, the guitar solos at the end, which are the climax of "Venus Isle", are just embellishments over a chord progression that is inherently appealing and ascending, which Eric Johnson emphasized with the lyrics about ascent like "And blasted off to the stars." (
https://tabs.ultimate-guitar.com/tab/eric_johnson/venus_isle_chords_2249021) I could give many more examples of corroboration of my hypothesis, if needed.
Where does my hypothesis leave us with respect to the nuts and bolts of creation of spiritual music? (1) I believe the songwriter should first decide exactly which mood they want to convey: amount of power (4/4 rhythm is more intense than 3/4 rhythm, for example), clarity of ascent (I bIII is more obvious than I bVI), piquancy (in a major key, tastefully flatted notes like b3 and b7 are more piquant than 3 and 7), and so on. Both the chords and the scales used in the song are affected by this decision. (2) Select chords and scales that will match the decision in #1. (3) With the underlying theory of the song in place, then continue to match decision #1 with specifics such as instruments, amount of harmony, specific chains of notes, and so on. (4) Test the success of the resulting song on people, either by conventional responses (verbal, written) or (ideally) by measured neural responses, and then make corrections and learn what worked and what didn't, and why. (5) Refine the process and develop a similar theory for the most effective ways to chain together notes in a melody, with the goal stated in #1.