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I have a simple progression F#m > E with two bars to each in 4/4. If I play F#m pentatonic it sounds bluesy and with a bit of attitude, if I play the E major pentatonic scale it seems more "classical". The two scales sound different. Looking at the notes, neither of these scales have enough notes to say whether the tonal centre of the progression is F#m or E major but even without having all the notes does using E major pentatonic somehow imply E major more than F#m since it has the key notes from the E major chord? And conversely, does the F#m pentatonic scale imply F#m since it has the main notes of the F#m chord.

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    Does this answer your question? How to find a root note of an unknown scale?
    – PiedPiper
    Feb 11 at 9:35
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    Even a single note can define a tonal center. Play C for a few seconds. Now that's your tonal center. Whatever note comes next, will get interpreted relative to C. The F# minor pentatonic scale has the same notes as the A major pentatonic scale. Which notes of the scales do you play, in which order, when, how strongly, in relation to a rhythmic pulse? Feb 11 at 9:37
  • @piiperiReinstateMonica - yes, and no. I've been 'training' my absolute pitch over several years, and use a single note to check, each time I pass a piano. That note is C. However, I hear it as the M3 of key Ab. For what it's worth, it's the 1st note of a t.v. theme - 'Coronation Street' - (which I don't watch!).
    – Tim
    Feb 11 at 9:47
  • Then it seems that you have a chronic Ab syndrome? :) It is subjective, and I can force my mind to deliberately move the tonic somewhere else by simply imagining sounds and feelings. But generally speaking, I'd say that even a single note paints a picture, and you don't need to explicate an entire scale to have a tonal center. And it's subjective - you cannot objectively "calculate" the tonal center from given notes, there's always a listener who forms the perspective. The harmonic context is some kind of a probability field. You might calculate probabilities. Feb 11 at 9:55
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A short motif of only 2 chords often can't define the tonic. But if you have an entire song you can ask yourself:

  • what is the final chord of your song?
  • with which chord does it start?
  • is there a dominant tone in the melody?
  • where do you have a "home feeling" in the tune or in the chord progression?

There are surely many examples that are oscillating between 2 modes or keys (pentatonic or not). Just to name a few spontaneously:

  • Lady in black
  • a hundred miles
  • don't let me down
  • black is black

But the key of all these songs can be identified - some only by the continuation.

Probably we need more information about your song to tell you on what key it is based. E major has 4 sharps, F#m has 3 sharps, and both pentatonic don't have a D#. But what does it matter?

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  • By 'dominant tone', do you mean a note that may be root, or the leading note/tone, or the actual dominant note?
    – Tim
    Feb 11 at 9:49
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    Then we get songs in nebulous keys - Sweet Home Alabama comes to mind.
    – Tim
    Feb 11 at 9:51
  • no, I mean the repercussion tone which is usually the 5th (in modes) e.g.: B in E, C# in F#m Feb 11 at 9:51
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Let's check which notes they are.

E maj. pent. comprises E F♯ G♯ B C♯.

F♯ min. pent. comprises F♯ A B C♯ E.

Common notes are the same, except for G♯ (in E) and A (in F♯m).

It just happens that those two notes are definitive!

The 3rds in each case!

In key E, there's G♯, in key F♯m, there's A. So that's where the difference comes. The third of any key is maybe the most important, apart from the root, of course! That 3rd is the defining note - is it major or is it minor?

EDIT: there are always two keys which will contain exactly the same notes, especially in their pents. Take E pent. major, and C♯ pent. minor. Exactly the same set of notes, but usually, there are clues as to which key they belong to. Various clues such as 'resting place', 'feels like home', cadences, et al.

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  • The 3rds are important in determining if the scale is minor or major arent they? In this case I am asking about whether the choice of pentatonic can influence the perception of tonality. If the F#m pentatonic is missing the 3rd (G#) of E major then using it to play a melody over the progression doesn't make the E major chord any less "major". We know the chord is not E minor so the 3rd is irrelevant in the melody isnt it? In this progression the note that is the important one is the D or D# and that is missing. THat is the defining note, not the 3rd of the scales in question.
    – armani
    Feb 11 at 10:51
  • @armani - I think I know what you're asking. There are defining notes. Root is an obvious. 3rd is another, and leading note comes into it. Passing notes play their part too. And which note is used on beat 1 in a bar. It makes sense that in an E bar, all I quoted will work anywhere, and the sam e for the F# bar. The awkward (maybe) is fitting A into an E bar, and G# into an F# bar. Not impossible, by any means. If that's what you're getting at.
    – Tim
    Feb 11 at 11:04
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In general, a collection of notes cannot define a tonal centre.

If we take just "the notes in the C major scale" as a collection of notes (and remove any indication that C is the tonal centre), then depending on the phrasing and cadences you create, that collection can be used as C major (with C as the centre); D dorian (with D as the centre), E phrygian, and so on. And the same logic will be true of pentatonic scales, or any other scale - what's percieved as the tonal centre is going to depend on the phrasings you use.

The only time a collection of notes can define a tonal centre is when there's only one note in your collection. If your scale is just { A }, with no other notes in, you're going to have a hard job creating the impression that any other note is the tonal centre. (Even then, if you were synthesizing the note, you could do it by emphasizing certain harmonics...)

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    Let's take C D E G A (or A C D E G) - Cmaj. pent. or Am pent.. I guess those are the only two options for that set of 5 notes? Or are there modes of pents? Asking, 'cos it's not something I've met yet. Modes of major work fine (except Locrian!), but pent. modes? Maybe not - no leading note/tone.
    – Tim
    Feb 11 at 10:16
  • @Tim I don't know if anyone actually calls them modes, but I'm pretty sure you can play the group of notes {C D E G A} such that any of them sounds like the tonic.
    – topo morto
    Feb 11 at 11:53
  • so if it is about the phrasing then lets say the melody starts on F#m and ends on E then according to you, the chord progression must be some kind of E. If I had all the 7 notes of the scale I would know but I don't as I only have 6 notes (2 pentatonics) and no D or no D sharp to know if it is E mixolydian or E ionian. My ear tells me that when I play the E major scale over this progression it sounds more like E major is the mother key, when I play the F#m pentatonic scale I hear E mixolydian as the key. Is this how it should be?
    – armani
    Feb 11 at 17:24
  • @armani "lets say the melody starts on F#m and ends on E then the chord progression must be some kind of E" - well, maybe, though the way phrasing relates to perceived tonic is more complex than just how the phrase ends. "when I play the F#m pentatonic scale I hear E mixolydian as the key" - I don't see why that would be, as there's no D in that pentatonic scale that would be characteristic of the mixolydian - but if that's what you hear, it's no-one's business to tell you you're wrong!
    – topo morto
    Feb 12 at 7:15
  • You are right, I shouldn't have said Mixolydian. forget that please. My reasoning is that when I play the F# pentatonic it has the notes F# A C# which belong to F#minor whereas if I play E major pentatonic, the E major chord tones are present and that tells your ear something doesn't it? My question here is basically, can the progression sound like F#m even though there is no D or D# in the melody and EVEN if the phrase ends on E? T
    – armani
    Feb 12 at 17:30

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