Help with determining the key signature of a new song that I am writing

Question

I recently wrote a chord progression for a song that I am working on. I just had the basic melody in my head and found the chords on the guitar, but I can’t seem to fit the progression within any single key and, because of that, I have really been struggling to finish the song. I would really appreciate any help figuring out this dilemma. I understand some music theory, but studying modes and key signatures has only confused me further because the progression doesn’t fit into any specific mode or single key.

Ok, so all of the chords are major and the progression goes as follows;

(First Pattern, played through twice) F# major A major B major F# major

(Second Pattern) D major A major C major G major D major A major B major

After the last B major chord, the progression returns to the top. The timing and rhythm is not super basic, but I can break it down and tab it out if anyone thinks that would help. I just figured that it would be better to start with just the chords and then I can include the rhythm or whatever else later if any of you think that it would help.

Thank you very much ahead of time for any help that you can offer.

Answer 1

I really like this progression, and I think it's useful of thinking about the whole thing as focusing around an F♯ tonal center. Major or minor? It's a little hard to say. The notes that are compatible with every single chord are F♯, B, E, so there's room for both major and minor. The resolution is to F♯Maj, but these progressions could very well have resolved to F♯min instead.

Here's my overall summary: the song is in F♯min, but with the i chord replaced with F♯Maj instead of F♯min. The first section draws on the family of chords in F♯ Dorian minor (with the i chord replaced by F♯Maj), and the second section draws on the family of chords in F♯ Aeolian minor (again with the i chord replaced by F♯Maj).

To start out, I think it's worth emphasizing that a song in F♯ Major can contain an A♮, and this makes sense on a theoretical level. Granted, this might seem to go against classical music theory, since A♮ is the flat third and any major scale should contain the major third. However, the F♯ Major Blues scale contains the notes F♯-A♮-A♯-C♯-D♯, where A♮ is a blues note. Your progression (and many other similar progressions) builds off this idea. The second chord of the song (AMaj) is built from that blues note (A♮), and that note (A♮) will work melodically over every chord in the song. This makes F♯min pentatonic (F♯-A-B-C♯-E) a great candidate for soloing/writing melodies. That one scale would sound good over the entire first progression, and it could give some nice continuity to the melodic phrases. (As an aside, it would also sound great to play F ♯Maj pentatonic - A Maj pentatonic - B Maj pentatonic, but this isn't the cohesive description you're seeking. Or you could even play F♯ Maj pentatonic over m. 2-3 and F♯ Maj pentatonic over m. 1 & 4.)

So, I would describe the first section as I-♭III-IV-I, with the note that I-♭III doesn't really disrupt the presence of a single tonal center.

As for the second section, I think it mostly fits in this same idea of F♯Maj/min. Just as F♯Maj-AMaj-BMaj-F♯Maj sounds great, so would DMaj-EMaj-F♯Maj. (This ♭VI-♭VII-I progression is part of the Mario Bros. theme song.) However, two chords (CMaj-GMaj) are an exception. These chords don't support an F♯ min pentatonic melody, and they don't really fit into a description of the song as being in F♯ Maj. Accordingly, their function can be explained as a parallel movement. Essentially, you're repeating the DMaj-AMaj (♭VI-♭III) progression, just down a whole step. That sort of technique sounds great when well-placed, as it is here, and it's a good tool to have in one's bag of composing tricks. So I'd describe the second section as: [♭VI-♭III in F♯]-[♭VI-♭III in E]-[♭VI-♭III in F♯]-IV.

Overall, here's how I'd suggest thinking about this:

• 1st section is I-♭III-IV-I in F♯
• 2nd section is ♭VI-♭III-[♭VI-♭III in E]-♭VI-♭III-IV in F♯

If you want to go deeper into other chordal options, you can think of it like this:

• 1st section is in F♯ Dorian minor, but with the i chord replaced with F♯Maj
• 2nd section is in F♯ Aeolian minor, but with the i chord replaced with F♯Maj

Accordingly, other chordal options available to you might include any progression in F♯ Dorian minor or F♯ Aeolian minor, but with the i chord replaced with F♯Maj. For example:

• DMaj-EMaj-F♯Maj
• BMaj-EMaj-F♯Maj
• BMaj-C♯Maj-F♯Maj
• Bmin-C♯min-F♯Maj
• etc.

Answer 2

So, we have all major chords...

Part A

||:F# | A  | B  | F#:||

Part B

 | D  | A  | C  | G  |
 | D  | A  | B  |

I think you could analyze it...

Part A

F#: I bIII IV I

Part B

D: I V  bVII IV   
D: I V F#: IV`

Basically, you have two sections with two tonal centers (keys) and each section has a borrowed chord. The bIII and the bVII are borrowed from the minor modes of the respective keys. Some might like to say the B part is using the Mixolydian mode to get the flat ^7 triad or borrowing bVII from the Mixolydian.

There is no reason to bring in classical style modulation ideas like pivot chords and closely related keys. You can move directly into any key you like.

I think it's worth noting that you use a descending 4th root progression for several of your changes: B to F#, D to A, and C to G but not a descending fifth progression. I find that is pretty common in rock music. Borrowing bVII is common in rock too. Also the roots of your part A - F# A B outline the beginning of a minor pentatonic scale. Playing major chord on those roots in power chord fashion is also something I think you will find in rock music.

Another thing I noticed is all the chord roots are from the D Mixolydian mode - excluding on the E - D (E) F# G A B C.

If you re-analyize part A as...

B: V bVII I V

...and the transition from part B back to part A as...

D: I  V  B: V 

...you get all the chord labeled from the Mixolydian modes of B and D.

All together...

Part A

B: V bVII I V

Part B

D: I  V  bVII IV   
D: I  V  B: V 

Now we can see a pattern common to both parts: I V bVII

I think I like this second option better, because of the pattern, and because rock music is so heavily flavored by the Mixolydian mode.