Learning music in 3 seconds

All we need to know is the bass note. The bass note is just one note at the time. (We can't have 2 foundations or references at the same time).


Once we know or (define by composition) the bass we  just add the note numbers 1,3,5 with respect to bass. This is called the harmonic triad.


For example:


Bass C
Harmony: C E G


Bass F
Harmony F A C


Etc


(The first 2 measures of Imagine - John Lennon)


Refined music may have additional code to the basic 135.


For example the 3rd chord of Imagine is:


C9 ie
CED (D is nine scale steps above 9)


Other examples:



Huge first chord of Hey you - Pink Floyd


E9 ie
E bass and harmony G B F (F is F sharp as the scale is E minor)


Further reading:


Bach Bass Rules:


https://normanschmidt.net/scores/bachjs-general_bass_rules.pdf