I like this! I've always wanted to build a music theory textbook (like Laitz) where the examples could be played.
> When a song says that it is in the key of C Major, or D Minor, or A Harmonic, etc. this is simply telling you which of the 12 notes are used in this song.
Small nitpick, this is not accurate, C Major and A (natural) Minor have the same notes but different starting notes so they are different scales, and pieces written in them sound different from each other. It's one of those things that's slightly hard to explain if you don't sing/compose/play an instrument/read music but very obvious if you do.
If you optimized the tuning for harmony, the notes would be largely similar, but some of them would not line up that well. Playing one scale with you instrument tuned for the other wouldn't work that well.
Yes, I probably should have added "in equal temperament, ...". I would say that most of music theory assumes equal temperament because it's the simplest to deal with from a theory point of view, because it allows you to modulate to other keys with no restrictions, and because deviating from equal temperament is something that is more of the performer's choice than something the composer dictates. For instance when choirs hold some consonant chords (eg at the end of a cadence sometimes), we tune the notes in just intonation (ie away from equal temperament) to get the nice "ring", and barbershop quartets sing some intervals about one-third of a semitone differently from what equal temperament would be (https://en.wikipedia.org/wiki/Harmonic_seventh_chord), and leading tones are often sharpened quite a lot for melodic purposes; these adjustments are something that you do naturally on a continuous pitch instrument, and composers normally don't specify them.
I can explain it: if you drew a frequency graph of how often a piece of music in those scales used each note, the graphs would be different. The tonic (first note in the scale) would likely be the highest point in the frequency plot. The note seven semitones up would also likely be prominent.
Perhaps even more important, the tonic will be used as a place of repose, or resolution of tension. Most traditional tunes end in the tonic, and the majority begin in the tonic as well. In addition, the major and minor modes have been used to convey different emotions, that will probably be invoked at some level if you've been exposed to a reasonable amount of mainstream Western music.
I suspect that there are no first principles that explain these traditions (and many more), but they work well enough that they can be relied upon (for instance) to reinforce the emotional experience of a movie, sports broadcast, or religious ceremony.
Perhaps a psychological effect worth exploring is how we remember aspects of music, and how that memory shapes our experience of new and familiar music.
Counter-counter nit pick: it's still not accurate because a piece that stays in C Major all the way through can still use notes outside of the C Major scale (eg passing notes)
Also I would say "X is simply Y" means "all X does is Y", but I guess this isn't universal
>Small nitpick, this is not accurate, C Major and A (natural) Minor have the same notes but different starting notes so they are different scales, and pieces written in them sound different from each other.
Only because they follow usual (classically derived) patterns about the chords played in each key (e.g. 1st, 4th, 5th etc, with are different in each key, and thus give different priority to each note of the scale).
One could play absolutely the same song in C major and A minor (same chords, not same relative chords) -- and it would sound 100% the same, the chords would just have different relationships with each key.
Yes, but a musician would (reasonably) say, for example, "this song is in CM, not am". I'm trying to say that keys are traditionally defined to be more than "what notes are used"
The chord relation 1st - 4th - 5th is derived from the natural overtone series every vibrating string or air column emits.
Every human can deduce unconsciously the base key note of a song by hearing the song.
This is a adaption to physical laws not a cultural convention.
> When a song says that it is in the key of C Major, or D Minor, or A Harmonic, etc. this is simply telling you which of the 12 notes are used in this song.
Small nitpick, this is not accurate, C Major and A (natural) Minor have the same notes but different starting notes so they are different scales, and pieces written in them sound different from each other. It's one of those things that's slightly hard to explain if you don't sing/compose/play an instrument/read music but very obvious if you do.