Recognising Keys by Chord Sequences

How to recognize the key of a song by looking at its chords? Get the trick there! :)


View the full lesson at Recognising Keys by Chord Sequences | JustinGuitar

Hi Justin and team, just wanted to check question 4… Couldn’t Eb, Ab, Fmin also be found in Eb Major (not just Ab major)?

Yes, could the Fmin be either ii of Eb or the vi of Ab? hope that makes sense!

Hi kahunarory and welcome to Community. You are correct for both.

Thank you, starting to make sense!

Eb, Ab, F min=
Key of Ab, Bb, C Db, Eb, F, G, Ab
Key of Eb, F, G, Ab, Bb, C, D, Eb

Are both correct? I put Eb instead of Ab. In Ab we would say it is a V, VI, I progression
and for Eb we would say it has a I, IV, II progression?

In the key of Ab major, wouldn’t that be V - I - VI? Or maybe I misunderstood your question.

Oops, yes, V, I, VI.

So both Ab and Eb should be acceptable answers to number 4?

In this case I’d take Fmin as the starting point as it can be the II, III or VI degree. Ab and Eb (majors) can be the I, IV or V.

As Ab and Eb are not adjacent, one of them must be degree I.

  • If Fmin is II, then Eb is I.
  • If Fmin is III, then Db is I.
  • If Fmin is VI, then Ab is I.

So I think yes, both solutions are possible in this case.

So there are actually 2 trick questions, not just the last one. Thanks!

Another trick for this is Ab is the 4th interval of Eb and Eb is the 5th interval of Ab. So this gives you
a solid starting point.
This is where knowing the Circle of 5th comes in handy.

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Thanks for the tip. I haven’t got to the circle of fifths yet.

Hi Justin and team,
Great lesson! I threw a dart at my music collection and hit on Low, by Cracker. I figured out, based on the song’s chords, it’s in the key of G. I noticed the lead guitar is using the Em Pentatonic scale. You touched on this a bit, but why does that work so well over a song in G major?

@AdrienneG

G major and E minor are relative major / minor to each other. The G major scale and the E minor scale share the same notes. The key of G major and the key of E minor share the same chords. The G major pentatonic and the E minor pentatonic scales share the same notes necessarily.

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Thank you Richard! Of course I probably should have recognized that by looking at my charts, but it just more fun to connect with the community. :wink:

You’re welcome @AdrienneG

Also - are you sure about those chords / that song?
I don’t know it at all but a quick web search suggested the key of E with some out-of-key chords.

Pretty sure it’s in G (D, C, E, G) with E being the major VI.

Hi @AdrienneG You may be right. I don’t know the song and didn’t spend much time looking.
If in the key of G …

G = I
C = IV
D = V
E = VI (a borrowed chord).

Addendum.
I have just watched an acoustic cover. The chord sequence (for the whole song) runs D, C, E, G and that G chord at the end of the sequence does sound like home, the tonic. So I agree with your take on it.

To return to your question about scales then.
You can happily use the G major pentatonic (if you are new to these scales think of the same shape as the open position E minor pentatonic pattern Justin teaches in the beginner course) apart from when the E chord is being played. You need to adjust and avoid the clash of the G# note in the E chord and the G note in the G minor pentatonic. Unless, of course, you play those notes against each other and it sounds good, in which case happy days. If it doesn’t sound good, make a quick switch to either E major pentatonic or E major arpeggio or E major triad notes (chord tones) when the E chord is playing.
Hope that helps.

Cheers :smiley:

| Richard_close2u | Community Moderator, Official Guide, JustinGuitar Approved Teacher

Thank you Richard! This is super helpful. I was getting a bit ahead of myself, as I just finished theory module 4.2 and recently completed Justin’s beginner course. I look forward to taking the next steps, like into minor keys. :grinning:

At 2:05, Justin plays a solo from a popular song. What is the name of the song? Thanks