Is there a simple technique to construct or memorize chord pattern of a song If I know the main chord of a song? Also, how to guess the next chord while playing a song. Specially with a guitar.
I know with practice you can get expertise on playing song by ear accurately. For a beginner, please share your experience or guidance how to learn play by ear without notations.
Studying music theory is exactly what you are looking for.
People tend to think of music theory as the rules of music but it is not. It is just the study of what has happened in the past, and a good way to learn what is common, and what is common in a certain style of music.
If you understand this it will give your ears a crutch to help you guess what the other chords might be.
A very high level example is if I know the main chord as you put it is C and assume that the chord's root is the key I am in (C) I know there is a good chance that the other chords are diatonic to that key. So if my main chord is a C maj triad I can assume that the chords being used would be G Maj, F maj, d min, e min and a min. So those are good to start with. Not all music will always use only diatonic chords, or be in a major key, but you have to start somewhere.
Along with music theory learning other songs in the style that you want to play is very helpful because without real world examples, and knowing what the theory sounds like, it is not very useful. So learn a little theory, try to apply that theory to song you like. You will quickly find you don't understand why something doesn't fit in with the theory you know, so learn why what you don't know. (Why am i getting a Bb (b flat) chord that is not in the key...well, it is not but it is common, in rock and pop, to borrow this chord from mixolydian. How do i know this...well I studied music theory)
Rinse and repeat for the rest of your life. As you do this, your ear will get better, you music theory knowledge will get better, and you will become a better player, musician and composer.
A lot of the simpler songs will have 3 chords - generally I, IV and V. In key C, C F and G
When the song is on one of these, and the player feels a change coming - which can happen naturally, otherwise comes with experience ( often called practice), there is a 50:50 chance of getting the next chord right by accident. As in, you're playing C, and you feel a change, there's only F or G that could fit (in a 3 chord song, obviously). After that change, there's still a 50:50 option for the next.
Let's face it, if the wrong choice is made, it's pretty easy to play the correct chord, albeit a little late! But how to get it right first time?
It's usually down to having played hundreds of songs, and there's a feeling that comes as to when the changes occur, and what they'll be.
Throw other chords into the pot, and the first that will be there are minors. Three of them, and there's often a feeling that one is coming in a song. So, 33% chance on this. Still pretty good odds.
By listening to many songs, and writing down what you think the chords might be, you'll improve. Also, take songs you already know - Happy B'day, children's songs, national anthem, and play slowly, in whatever key, knowing what choices of chords will most likely be available in that song.
Different styles/genres of music have different common chord progressions. To be able to guess and memorise chords for all styles, you really have to spend a lot of time studying. However, you can start understanding the 'vocabulary' of one style much faster.
When you listen to a song, first thing to do is know what key/scale it is in, then:
The melody is the scale's 7 notes.
The harmony is the scale's 7 diatonic chords.
If you know the chords beforehand, then you can figure out the key as well. For example, if your song had the chords C,F,G then there's a good chance it's in C major, which correspond to the I,IV,V chords.
Also each of these diatonic chords has a certain function in a song. The more you play by ear, the more you will hear the functions. For example, the fifth chord (in major) has the function of wanting to go back to the one chord which produces a sense of relief. You will also find that alot of songs have a repeated chord progression. For example, in Pachelbel's Canon it's I-V-vi-iii-IV-I-IV-V.
This is a simplification, but I find it to be the case in the majority of songs I've come across and I only play by ear.
