That's quite a broad question, another Sean, but I'll try and help. In my opinion, for music to flow naturally, it has to be learnt like a language and this requires a lot of ear training. The first step I always advise is to attempt to work out simple melodies by ear. This could be theme tunes, nursery rhymes, basic riffs - whatever - but one has to go through this process to understand music on a functional level.
A good analogy of this is that when we talk we form sentences instinctively; we don't struggle unless it's a language we don't know or barely understand. First and foremost, music has to be learned like we are communicating with someone, and there is a similar structure. Just like the written word has sentences, punctuation, paragraphs, etc, well so does music. When one learns to play without our thoughts getting in the way (just like language) well then you can truly express yourself. Ear training and working out songs by ear is paramount when it comes to taking ideas from your head and putting them straight into your fingers. This translation process becomes more instinctive and natural over time.
With that said, here's some basic rules of harmony:
First of all learn your diatonic keys. Start with the major key (the backbone and DNA of all western music). To create the major key we need to understand some basic concepts of music, starting with the notes that exist. These are:
(A), (A#Bb), (B), (C), (C#Db), (D), (D#Eb), (E), (F), (F#Gb), (G), (G#Ab)
Notice there isn't a (B#Cb) and there isn't an (E#Fb). These can exist in certain keys, but the notes don't physically exist on instruments. All the notes that are shared between brackets are called enharmonic equivalents and are literally the same note/sound. You may question why they have two names, but the reason is quite simple: it's to make music easier to write down.
With the notes now known we can apply a formula. We will start with the major scale which is:
T T S T T T S (T = Tone S = Semitone)
You must first memorise and internalise this sequence. To create a key we must understand what tones and semitones are. A tone is an interval - or gap - of two notes. In other words, if you look at the notes above and start on A, a tone away from that would be B. A semitone away from A would be A# or Bb; both would be correct, although when writing diatonic keys, you should always pick the note that is the next letter in the alphabet.
So, if we follow the formula for the major scale, we should end up with these notes:
View attachment 25766
(I've inserted a picture of my original text as the alignment was lost after posting).
You should always start and end on the same note. Once you have these notes you can turn them into chords by following this sequence:
Major, Minor, Minor, Major, Major, Minor, Diminished.
This means the chords in the key of A are:
A major, B minor, C# minor, D major, E major, F# minor, and G# diminished.
Many songs follow the same progressions so it's good to get familiar with some standards first. We write chord progressions down by labelling each those chords with a Roman numeral from I to VII.
One of the most common pop progressions is this:
I V VI IV
In the key of A the chords would be:
A major, E major, F# minor, D major
A ballad sequence made popular in the 50's is this:
I VI IV V
Giving the chords:
A major, F# minor, D major, E major
Jazz commonly follows ideas around a II V I sequence.
The first thing you should do is put some chord progressions together yourself by choosing a key and using your ear to join chords together. Once you have done this you have to sing a melody over the top of the chords to create a harmonising theme. This is primarily what people follow when they hear a song as it's the main melody. The chords are considered to be an accompaniment. There's a lot more you can do from here to take your music to the next level including the use of extended chords, chromatic chords, borrowed chords/modal interchange, secondary dominant chords, altered chords, etc.
The use of rhythmic ideas is also crucial and is foundational to music. I can explain more of this at another point as I have to leave now and this post took forever to write
. I have no idea what you know and what you don't so I've started from the basics.
. 
Member
