I've been recently wrapping my head around the analysis of the following progression: F Dm Am C. Would you agree it's got an undeniable lydian vibe? I know an explicit lydian progression should feature #4 (and therefore the lydian mode would have been clearer if the progression had featured a G or Em chord) and in fact this one doesn't, but for some reason my ear can't help perceiving that F as the "home key". Maybe it's because the final C chord implies the #7 (#4 of the F lydian scale)? Or would you disagree and say the progression is just "straight" Am? To add even more ambiguity, since the fourth degree of the scale is not explicited, it could also be considered to be in F major. But this option is definitely put aside by the second section of the song, going F Am G G#dim (and thus straight harmonic minor). So wrapping it up my analysis would be: first section sounds halfway between lydian and aeolian (but with a slightly more prominent lydian vibe), second section resolves the ambiguity going straight harmonic minor. Would you agree?
The song in question is Galantis-Runaway:
QUESTION EDIT: First things first, thank you guys for all of your answers. Each and everyone has been very useful.
I think we've come to a point, however, where it might be of some importance to clear out the reason why I came up with the question in the first place: the very ultimate purpose of my analysis is that of "mining" the relationship between melody and harmony here. My "compositional routine" would often be the following:
1 come up with an acapella vocal line entirely in my head" 2 put it into midi and see what scale/scales it fits 3 come up with a chord progression to transform the vocal melody into a full song section.
So the matter here would be not just simply "harmonizing a melody" (you can just throw tens of progressions under your melody and come up with something pretty coherent and structured) but rather "finding a chord progression that REALLY makes your melody stand out".
So there are many people out there stating that one of fhe most used tecniques in this sense is some sort of modal overlapping, meaning that the composer would often choose a key, write a chord progression in one of the seven modes in that key, and then create a melody in a mode other than that of the progression (though still in the same key), meaning, of course, that the melody would imply mainly and resolve ultimately on notes belonging to a chord which is different than the "home chord" of the progression itself. And the process would also work backwards (starting from the melody like I do).
Such a method would inevitably imply a couple of crucial points: 1 position matters. In both harmony and melody. 2 one can always tell what mode a progression is written in (by "progression", i mean the nude and simple progression).
And the two intertwine, since, even in a progression like this one (F Dm Am C), though characterized by a level of ambiguity undeniably higher than average (mostly due to to the fact that it does not contain the full tritone, as many of you pointed out), there actually is something that makes a chord prevail on the others and stand out as the "home chord", and that something is position: in absence of any other stronger elements driving the attention of the ear, the first chord prevails. The whole strenghtened by the perfect cadence at the end of the progression (C F).
This is the point where many would state that just the fact that a progression begins on a certain chord doesn't automatically imply that that chord is the home key. Which is true, but only in absence of any other "strong signs" of a different home chord (like a cadence, or the repetition/long duration of that other home chord), which is not the case here.
So this is why i wouldn't consider THE PROGRESSION itself to be in A minor. I wouldn't consider it C major either, because the only Cmajor chord falls on the fourth beat of fhe bar, which is the weakest of the four downbeats. What is more, all its chances to be heard as the home key are kind of "sucked away" by the fact thay it's involved in a perfect cadence as dominant key.
So, to wrap it up so far: Is this progression ambiuguos in a sense that it doesn't clear out its triton? YES
Is this progression ambiguous in a sense that the listener cannot easily identify a home chord? NO.
I would call the first "formal" or "abstract" or "theorical" ambiguity, and the second "practical". So this song progression is FORMALLY ambiguous, but not PRACTICALLY.
Does the verse of this song (no need to argue with the chorus, since it's clearly in Am) really "give justice" to what would otherwise be a pretty "vanilla", boring, even childish vocal melody in Am, ultimately making it stand out and giving it a unique flavour? YES (song is a banger).
What is this due to? The fact that it mixes up a minor (or better Aeolian) melody with a progression which is INHERENTLY in F.
What is ultimately ambiguous in the progression is not its home chord, but its MODE.
The note B then appears in the following section (chorus), creating some sort of resolution to the tension previously caused by the ambiguity, clearing out that the progression is lydian. Which has even a stronger impact if we consider the fact that the song has an ABAB structure, meaning the listener will be approaching the same F Dm Am C progression in the second verse, but this time with the "psicoacoustic advantage" of still having that B from the chorus "in his head".
PS: psychoacoustics (which i find incredibly useful when it comes to explaining harmony) may also have some further implications in the matter: it is not completely true that the progression F Dm Am C has neither B nor Bb: the G note in the Cmaj chord and the E note in both the Cmaj and Am chords actually have B as their third and fifth harmonics, which, in absence of any materially played Bb in the chord, simply prevails, ultimately giving the progression a (though incredibly subtle) INHERENT lydian vibe.
Do you guys agree?