u/Musicman2568

Suppose I know the notes of a particular sequence, and that sequence has a note or note(s) that are non-diatonic to the key of the overall song.

I assume this means there has been a modulation of some kind. I am learning (through another thread I posted on r/piano) that you need to use your ears to determine what the key of the part of the song you are in is, and then you can more accurately use that context to determine the chord progressions.

Take for instance, this song:

https://www.youtube.com/watch?v=4liWweR89uo

In another thread, it was pointed out to me that the first four measures sound like they are in the key of F major, and also that all the tones are diatonic to F major, so its likely that part began in F major. Hence, we would interpret the progression as being in the key of F and name the chords accordingly. Separately, someone argued it is in the key of C major.

I, on the other hand, erroneously assumed that because the overall piece is in G major, and the notes in the first four measures are diatonic to G minor, then its not a shock that the song begins in the parallel minor.

Of course, my analysis omits what I actually hear to determine the key, which I know is far more important then just figuring it out on paper/logic like I did.

But what am I supposed to be hearing to determine the key? I totally understand that a key is the center, and its what a sequence resolves to. If we look at measures 5 and 6, I can definitively say that those are in the key of G major even just using my ears, as both measures so strongly resolve at G, and well, the piece is in G major (correct me if I'm wrong though).

But what about the first measure am I supposed to "hear" that tips me off to it being in Fmajor?

I am really struggling to identify the chord progression from a piece.

First: Yes, I can read sheet music. Yes, I know my chords, honestly quite well. If you ask me to name the notes of any major or minor triad, any major/minor/dominant 7th, and in any inversion, I can do it easily/play them easily on the piano AND the guitar pretty much instantly. I also know about other chords like diminished, augmented, sus, add, 9, 11, 13. Now I'm not going to say I can instantly recall these but I can easily derive them.

Despite this, if you hand me a piece and ask me to tell you the chord progression from the sheet music, I never can do it. It seems like absolutely no song, no matter how basic, uses chord progressions with "obvious" chords. It seems like there is always some omissions, always some strange tone added, etc.

My process for attempting it is this:

1. Identify key of song to help determine context (I use the key signature and then play a bit of it to see if it resolves to the major or minor of that key signature)

2. For each measure, identify all the notes being played (and I do this across both the bass and treble clef)

3. see if the notes played belong to any of the diatonic chords. If not, consider the chords within the parallel or relative minor. if not, consider things like secondary dominants.

4. So often it seems like the chords played omit certain tones, and so I consider if perhaps the chord is omitting the 5th say in a 7th chord, etc.

I literally get nowhere with this method. I am clearly doing something wrong. I also don't know when a tone should be considered a "non-chord" tone and thus ignored from this "analysis".

Let me do an example from a pretty basic piece, which to me seems to be in G major:
https://www.youtube.com/watch?v=4liWweR89uo

The first four measures are playing CFG and CDF. The key is G major, and since these are natural, I would think maybe these chords come from G minor. In G minor, C F, G is what I would call Csus4. Also in G minor, we have C D F which would seems to remind me of a Dminor7 with the fifth omitted. SO would I be write to say this piece, which is in G major, begins in G minor with a Csus4 leading to a Dmin7 (omit 5)?

Continuing on to measure 5, we have C and E in the treble and C, G, A in the bass. In the context of G major, especially with the ii7 being A minor, I can't imagine this being anything else besides Am7, which from my knowledge consists of A, C, E, G.

IN measure 6, B, A, G in the bass, D in the treble. To me, G, B, D, is obviously a G major chord which is diatonic, but what the heck is that A doing in there? How would I interpret that. My best guess here is that this is a Gadd9.

I mean we can continue here, but I want to know the following:

1. Did I do this right?

2. Is my method a good one?

3. How do you know when to ignore a tone as a non-chord tone and thus omit from this analysis? If a tone is intentionally selected by the composer to not be a chord tone, then this would lead me to a faulty conclusion about the progression.

4. Is it possible for there to be multiple "answers" where two people derive the chord progression, are effectively saying the same thing but doing it differently?

PS: I have a teacher, she just wants to focus on learning piano technique/mechanics for now AND studying theory independently, and she says we will apply it to songs starting in 6 or so months... but I'm an engineer by trade so not understanding this stuff drives me crazy because i always need to know what i'm doing/playing.

In this video, at about 2:39, you'll see it shows the "magic chords" of the a minor pentatonic scale. These chords clearly sound very nice with the melody, and I get its because these chords have notes that mainly have the pentatonic scale in it (I see F major listed in it which is strange but maybe someone can explain that).

For reference in case you don't want to watch the video, the video says for A minor pentatonic, the "magic chords" are C major, G major, A minor, F major, D minor, E minor.

I'm just really struggling to figure out, say for example, if in the key of D, I want to play the D minor pentatonic, how can I find these "magic chords"?

Video link:
https://www.youtube.com/watch?v=9qSET19oZW8&t=17s