I am trying to learn piano by myself and have been studying a little bit of music theory. But I still haven't faced anything concerning how to create chord progressions and how to choose chords for a song. How do I begin? Any suggestions of topics to search, books, online content, etc.
You read the sheet music/chord charts/whatever of lots of songs. And listen to even more songs.
It's really the only way. Lots of 'theory' tries to explain what composers HAVE done successfully. But it's all pretty crap at suggesting what YOU should do. You'll have noticed all the 'why does this work?' questions here from people who have encountered something outside their particular world of 'theory'. Patterns emerge, but there are SO many ways of making patterns!
This is one of those things that is very dependent on style. A modern r'n'b song is going to have different typical chords to an MOR piano ballad, which will be different to a grunge song.
If you're not already, learn to analyse existing chord progressions so that you can understand what degree of the scale chords are based on (so you can identify chord I chord V, etc). This gives you a common basis to compare and contrast chord progressions.
Then - learn some songs, focusing on their progressions. Learning a bunch of songs in the same style will help you see what the typical 'pallete' of that style is. You may need to think in terms of modulations or borrowed chords to make sense of some progressions.
Start with a simple song of any key you feel comfortable with. Identify the tonic(I), Sub-dominant(IV) and dominant(V) of the key. These three degrees have the easiest chords. Practice the tune/melody with your right hand and note down to which degree each of the notes in the melody belong to. Then you can build patterns like this:
If the note in the tune is tonic(I),mediant(III) play the tonic's chord with left hand.
For supertonic(II),dominant(V) and leading note(VII) try the dominant(V) chord.
For sub-dominant(IV) and sub-mediant(VI), play sub dominant(IV) chord.
Do not overdo this every time you hear these notes. As a starter, Try to change chords on the first beat of the bar. Then according to time signature, you can try different patterns of chord progressions.
You'll find that a lot of the more simple songs have three chords in them. In major tonality, those are I, IV and V. Put in key C, that's C, F and G. A lot of songs start on the tonic, so for a song in key C, that will be chord C.
Listen for where a change of harmony happens. At that point, in a three chord song, there's a choice of two - IV or V. 50:50. Good odds, and by listening carefully, you'll be able to decide which fits. One will, the other usualy won't.
In diatonic songs, there are three other chords which may be used - ii, iii and vi. Again, in key C, that's Dm, Em and Am. You need to be able to tell whether a chord is major or minor. If a change goes to minor, there's only three to choose from. Still narrow odds.
Another way is to map out on paper, while listening. Four bars on each line works well. Only listen to the tonic chord, and fill that in for each appropriate bar as the song plays. That will help to ascertain what the missing chords may be.
All this is basic, and it's best to get good at this, before moving on to more complex songs.
Each key has 3 functions.
Say Key of C major CDEFGABC
The deepest level of meaning is 3 functions .
Tonic relaxed [ home] hero Subdominant journey ( motion) Dominant tense ( villian)
So the key of C major has 7 diatonic chords .
However those 7 chords fit into the 3 functions ( groups )
All chords in the same function shate the same meaning .
Even though a key has 7 diatonic chords ( that fit in only 3 groups )
That does not mean there are only 7 chords in the key though .
Actually all 12 notes are in the KEY of C major and almost all chords are in a KEY also.
It works the same way as the 7 diatonic chords work
( it all fits into 3 functions)
In the key of C major
Tonic function chords [ home ,still,the hero relaxed]
I.Cmaj7 [ C6 ] iii.Emin7 [ G6] vi.Amin7 [ C6]
Subdominant function chords
ii Dmin7 [ F6] IV Fmaj7 [ F6]
V7 G7 vii% Bmin7b5 ( Dmin6)
The 3 functions are combined to create 3 functional blueprints that all chord progressions are made from ( and all song sections )
Tonic / Subdominant/ Tonic Tonic/ Dominant/ Tonic Subdominant/ Dominant/ Tonic
These 3 functional blueprints combined make up every song section that exists .
Lets see example in the KEY of C major . ( just plug chords from each function )
First functional blueprint is Tonic / Subdominant/ Tonic ( this means relaxed or home then journey then back home it gas some harmonic motion but very relaxed feeling )
Tonic/subdominant/tonic Cmaj7/Fmaj7/Cmaj7 Or C6/F6/C6 Or Amin7/Dmin7/Emin7 Or Emin7/Fmaj7/C6
The next functional blueprint is Tonic /Dominant/tonic ( this means establish a hero then defeat the villian then go back home . Also home to farthest from home to back home again this is more harmonic motion than the first giving a exclamation point to the final tonic ) Tonic/Dominant/tonic [ key of C major Cmaj7/G7/Cmaj7 Or Emin7/Bmin7b5/Amin7 Or C6/G7/Emin7 Or Amin7/Bmin7b5/C6 Or G6/G7/C6
The last functional blueprint is Subdominant/Dominant/tonic
This is similar to the last one except we start on journey then go farthest from home then defeat the villian landing on home .
This is less abrupt
Subdominant/Dominant/tonic [ key C major Dmin7/G7/Cmaj7 Or F6/Bmin7b5/Emin7 Or Dmin7/Bmin7b5/C6 Or Fmaj7/G7/Amin7
Next are examples of still the Key of C major However we are adding in all 12 notes to fully expand each function.
Tonic/ subdominant/Tonic [ key of C major Cmaj7/Fmaj7/Cmaj7 Or Amin7/Dmin7/Emin7 Or Aminmaj/F#dim7/F#min7b5 Or Bmin7/Bb7/C6 Or D7/Abmaj7/Amin6
Tonic/Dominant/tonic [ key of C major Cmaj7/G7/Cmaj7 Or Amin7/Bmin7b5/Emin7 Or F#min7b5/Gmin7b5/Aminmaj Or Bmin7/Ddim7/[cmaj/D] Or D7/Db7/C6 Or C6/Eb7/C6 Or C6/Fdim7/C6 Or C6/Fmin7b5/C6
Subdominant/Dominant/tonic [ key of Cmajor Dmin7/G7/Cmaj7 Or Fmaj/Gmaj/Cmaj Or Fminmaj/Gmin7b5/F#min7b5 Or Dmin7b5/Db7/[D7/C] Or Abmaj7/Abdim7/G6 Or Dbmaj7/Db7/C6
The KEY I,ii,iii,IV,V,vi,vii% Imaj7.......tonic iimin7........subdominant iiimin7.........tonic IVmaj7........subdominant V7................dominant vimaj7..........tonic viimaj7........dominant