Do you mean A minor as the vi - rather than the VI - of C Major? (Minor chords are conventionally notated as lower case letters when you're using Roman numeral chord scale position notation - or whatever that chord notation system is called.)

Do you have a link to that video? (hopefully in English, or with English subtitles) Also, if you can give the time in the video when he says this.

Without having seen the video, I'll take a stab at your question anyway.

I'm assuming by melodic or harmonic notes (and using A minor as the key), he means that instead of only using the A natural minor notes, a-b-c-d-e-f-g-a, you should also use the different notes from the A melodic minor scale (f# and g#) and/or the A harmonic minor (g#). He might be implying minor key music sounds more interesting with these notes - rather than just using the A natural minor notes.

He might also be implying A minor differentiates itself from C Major when using those particular notes (because without these notes, both keys' scale notes are the same.)

That is, if you're listening to a piece in A natural minor without those melodic or harmonic notes, and depending on the chord progression, your ear's sense of tonal center could possibly be C Major rather than A minor because these two keys use the exact same notes (or it could fluctuate between the two relative keys C Major and A minor - again, depending on the chord progression.)

But if you throw in a chord that uses, say, the g#, like the chord E (major), that leading tone g#, when it resolves to the note a, (say, when the chord progression goes from E to A minor, or E7 to A minor) that eliminates any tonal ambiguity between C Major and A minor - clearly establishing A minor as the key (and a as the root note) to your ear.

Does that make sense?

So after writing all the above, I listened to Darkside (which is in the key of E minor, not A Minor, and seems to have only E Natural minor notes in it - no harmonic minor or melodic minor scale notes). I can hear a slight ambiguity in tonal center when the chord progression goes from i to III, which it does often. When i plays, it sounds like the tonal center, but when the chord changes to III, it sounds like the tonal center. Is that bad, musically? Not really. But had the song used a V chord, using the leading tone d# in a B Major chord, somehow, that certainly would have shaken things up a bit, harmonically! :-)

Here's a link to Darkside :

It makes a lot of sense to say that A minor is the VI of C major, and that they are harmonically strongly related. In music theory we call these (A minor and C major) examples of 'relative keys'. They share the same key signatures (sometimes called 'accidentals'). Relative keys are always found using this VI-link (e.g. B minor and G Major are relatives too). This link can be heard in lots of music. E.g. Bach's first invention is in C major, but contains a significant development in A minor, and that was written around 1720.

300 years later, David Guetta (EDM producer) uses relative keys too, see the video from 10:31 onwards:


He makes a mashup of 2 songs, the first one is in A major, and he proceeds to one of his future rave songs, he chooses one that is in F sharp minor, exactly for same reason Bach did: they are relative. He explains it very well in the video.
The end of the video shows that transition when used on stage (A major -- f sharp minor, which is VI of A major) and how the crowd responds to it, see the video at 17:34:


There are many ways to incorporate this link into your music and make it work (John Miller also gave a great example). But I would suggest that you also try your own way of making it work.

Edit: timestamps seem not to work here. Sorry to post the video 2 times.

Thanks a lot guys! I think I was so confused because of the guy said whom I asked at first place. and that might be because the way I asked due to my lack of english skills..
I think I'm clear about what I wanted to know!
Sorry for late response I barely use soundgym nowadays.
Hope you all have a great day!