About Composing Melodies...

[Asterbee]

Has anyone here managed to succeed in this area? It undoubtedly seems to be the most difficult aspect of composition. Creating good melodies that are engaging and not repetitive/forgettable seems to be an increasingly rare compositional skill, as we don't see many games nowadays with memorable music that isn't just generic chord progressions.

[Master Mi]

@Asterbee
 

Composing good melodies, counter-melodies, bass lines, and drums is actually relatively easy to moderately difficult.
But writing interesting and harmonious chords is much more difficult and requires far more knowledge of music theory, experience, and musical imagination (but that's exactly where the great musical magic begins).

For starters, it is enough to know that in the Western tonal system there are a total of 12 notes (7 root notes such as C, D, E and 5 intermediate notes such as C sharp or D sharp) that repeat themselves in several octaves.

A piece of music - or at least a specific passage within it - always follows a specific key/mode, which always contains 7 different notes from the total of 12 notes within an octave.
These 7 notes (also spanning octaves) are essentially the key to the musical language in a musical work.

If you know this key (i.e., the key with the 7 notes), you already have a good foundation for rewriting or redesigning a composition according to your ideas without making your remix composition tonally inconsistent (finding the right rhythm is, of course, another field of musical art).

This applies to virtually all components of the composition, whether melodies, bass lines, or chords, although in the case of chords, certain minimum intervals between the chord tones should be maintained (this also applies to playing across octaves, whereby in the case of tone intervals, a lower C, for example, should be treated like a higher C).

While neighboring notes in a key (including notes spanning octaves, such as C1 + D2 or B2 + C4 in C major) tend to sound harsh and dissonant as chord tones, the 1st, 3rd, and 5th or, for that matter, the 2nd, 4th, and 7th notes within the key tend to sound more harmonious.

...

So let's assume that a piece of music is in the key of G major.
This key contains the following 7 notes:

1) G (1st note of a key = root note or tonic)
2) A
3) B
4) C (4th note of a key = subdominant)
5) D (5th note of a key = dominant)
6) E
7) F#
 

The tonic, subdominant, and dominant can be used to create interesting chord progressions, each of which fulfills different musical functions.

Tonic (1)= like a cozy home
Subdominant (4) = you're on your way to adventure
Dominant (5) = tension builds

A typical chord progression is, for example:

I - Tonic (1st note of the respective key)
II - Subdominant (4th note of the respective key)
III - Dominant (5th note of the respective key)
IV - Tonic (1st note of the respective key)

So, in the case of G major, a chord progression could look like this:

I >>> G + B + D (feel free to play 16 times in a row with a bit of groove and varying dynamics)
II >>> C + E + G (again 16 times)
III >>> D + F# + A (again 16 times)
IV >>> G + B + D (this time only 15 times, slowing down gradually, and on the 16th time, play the 3 notes one after the other to finish and add the root note D an octave higher as the 4th note). 

...

This is just a rough, hopefully helpful introduction based on practical examples.