Music Theory: Detrumining Key and Transposing Chord

Fiddling around on guitar, I’ve written two melodies that I’d like to combine, but I don’t know what key the first one is in or how to transpose the second one into the same key.

The first melody contains the notes F#, C#, A, and G#. (My guess is that it’s in the key of A major.)

The second contains and the open chords Am, D, Dsus, G and Em. (I believe this is in the key of A minor.)

So, what key is the first melody in, and how do I go about transposing the second melody into the same key? What if I wanted to go the other direction and transpose the first melody into the key of the second? Thanks.

Music Theory: Determining Key and Transposing Chord

The most likely key that your melody would fit into is f# minor. The second composition seems to be in a minor.

Which is a good thing, since i.e. both are minor compositions.

To transpose the tune from f# minor to a minor, raise all notes up 3 semitones which gives A, E, C and B.

To move the chords from a minor to f# minor, drop them 3 semitones: f# minor, B major, B sus, E major and c# minor.

Hope I’ve calculated that right!

The melody definitely works well in F# minor. The chords fit well as G or as its relative minor, E minor. (I’d be happy with A minor, except that the D/Dsus bit really wants to resolve to something with a strong G flavor.)

Try just dropping the melody down a whole step (giving E, B, G, F#).

In your melody, is there a strong sense of which note is in charge? That is, is there clearly one of those four notes that you want to have as the key?

Oh, and for the other direction: try taking the chords to Bm, E, Esus, A, Fm, with the key being A or F minor. The minor is a better fit, as the melody has the fifth of the minor chord (C# for this transposition) but not of the major chord (E for this transposition).

Your replies raise so many questions—the correct answer for which is “go to school,” but I would appreciate it if you’d continue to indulge me for just a few.

What about the first melody makes it in the key of F# major?

In the first melody, the dominant note is definitely C#. How does that affect your thinking?

I realized I forgot to include a chord in the second melody, it should be Am, A(add9), D, Dsus, G and Em. Does that make a difference.


F#minor is the relative minor key of A major, so (basically) contains the same notes. If C# is the dominant (note that dominant means the fifth note in the scale of whatever key the piece is in) then the tonic (the key-note) will be F#. The presence of an A natural note, rather than an A# makes the key F#minor rather than major.

As for the second piece I would agree with Pasta that it seems to be in Gmajor/Eminor (kind of hard to tell which without some melody, but assume its E minor for ease of transposition, it doesn’t really matter for current purposes). The Dmajor/sus going to G would imply a dominant to tonic (V-I) progression in the key of Gmajor. The A(add9) would be functioning as a secondary dominant (that is the dominant of the dominant). All you really need to worry about here is following Pasta’s instructions for transposition.

Sure - there is no simple answer. Modern music theory does have basic “truths”, but they are adjusted, bent and broken in every composition. But I’ll start with some anyway:

  1. A song has a home key (aka tonal centre). It starts in that key and will end in it.
  2. The key is major or minor and will use set of seven notes, i.e. a major or minor scale.
  3. There are a set of chords that can be built using those seven notes. These chords are “in the key”, but you will use other chords comprised of notes out of the key as well. (It’s already getting complicated!)
  4. The most basic chord is the TRIAD: one of the seven notes called the root of the chord, the note two steps up in the scale and the note two more steps up. e.g. 1/3/5 scale notes.
  5. The most important chord is the TONIC - it is based upon the 1st note of the scale (1/3/5). The other two important chords are the dominant (5/7/9) and the sub-dominant (4/6/8) (note than step 8 of the scale is equal to step 1 an octave up, and 9=2 an octave up). Jazz guys call these the “one”, “five”, “four” chords, and spell them I, V, IV.
  6. When you harmonize a melody with chords, the triad notes are the most important: they are usually the start/end/resting places of a melody.

So, when I said that f# minor was the most likely chord to fit your tune I was thinking of 6) because the chord f# minor is comprised of F#/A/C#.

Just realised, your use of the word “dominant” probably does not mean what I thought it meant. In classical music theory each degree of the scale (and the chord built on that scale degree) is given a name: I=tonic, II=supertonic, III=mediant, IV=subdominant, V=dominant, VI=submediant, VII=leading note. These days one tends to use the numbers rather than the names, but using the word “dominant” to meant the V chord is still common practice, so be careful with that or you’ll confuse over-learned musos like me.

Wow! I thought rock 'n roll was supposed to be easy. Do one hit wonder bands generally know this stuff?

Thanks for the music lesson.

Probably not. You don’t need to know any theory, you can just muck around until you find something that sounds good. It can be a bit frustrating when you start realising that you are continuously reinventing the wheel. You stumble across some really nice sounding chord structure only to find out later that it is one of the most common cliches in music.

I would have thought the best way for us to determine the key of the melody is to see the melody transcribed in full. Just seeing examples of some notes that are in the melody does not give sufficient information for making that determination.

I think.

So lets have the melody!


But what if I’ve written the world’s greatest super hit? Someone’ll rip me off! :smiley:

Here it is a simplified version in guitar tablature with the notes written above each strum for those who can’t read tabs (though I could write it out as sheet music, I’ve no idea how to type it).

First melody:

F# F# F# F# A A A A G# G# G# G# F# F# F# F#
C# C# C# C# C# C# C# C# C# C# C# C# C# C# C# C#


Second melody:

  A(add9)                       D(sus)

Am Am | Am Am Am Am D D D | D D D


G G G G G G G Em Em Em Em Em Em Em

Am Am Am Am Am Am Am D D D D D D D


Not to push my luck, but I’m toying with a third part that goes:

F# B G B F# B G# B E B G# B F# B G B

Thanks again for th help. Once I get the whole thing worked out, I’ll be sure to let everyone know when the song’s available on iTunes. :slight_smile:

What you’ve basically presented isn’t really a melody, at least in the traditional sense. These all sound like accompaniment, particularly the second one, which is basically a chord progression. The alterations (add9 and so forth) suggest parts of a possible melody, but you could play several different melodies over it. If this is a traditional song with vocals, the vocal part will be the melody, and that’s what will really distinguish the song. To convey that as written music, you really need a way way to notate time values, which conventional tablature doesn’t do.

Put it this way: I bet I could take your fragments here and assemble them into my own song, and that if we compare yours with mine, they’ll sound nothing alike. So no worries. :slight_smile:

That very first one is sparse enough that it could be worked into a few different keys. The most straightforward reading of it puts it in F# minor, though.

I haven’t looked in detail at the others. They’re not all supposed to be played at the same time, are they?


The second one seems clearly A minor to me. (BTW the other poster is right–that’s not a melody, it’s a chord progression.)


Finally, the third one is a good candidate for E major, though again, it’s so sparse it could be worked into other keys. It’s not a straightforward E major, anyway, due to the G natural. It’s like it switches back and forth from an E minor chord to an E major chord. But to my ear, it resolves on the E major, making it an “E major” piece overall.