I've been trying to brush up on my music theory recently, but I can't work out what key "Home" by Sheryl Crow is in. The chords are: G, Dm, Bb, C and F. It would appear to be C major, except for the Bb chord. Is it possible to substitute Bb for B dim, or is this actually in a different key?
There is no key which contains both G major and Bb major. Because that would require both B and Bb notes. It could be voiced as an A#, to fit the standard rule that a scale has each lettered note name exactly once.
The Chords describe these notes (although they may be 'spelled' differently, meaning Bb can be expressed as A#)
G, A, Bb, B, C, D, F
No standard 8-note scale contains four consecutive semitones like that. So there's two ways to understand this kind of progression.
A: There's some modulation going on.
If a chord belongs to the same key as the chord that follows it, then we are essentially changing to that new key (one that has the notes of both those chords).
If you're melody writing from this understanding, find a key for each pair of chords, and try to move to the new key by the end of each chord.
B: Defenstrated Theory.
It's quite possible that someone's sat down with an instrument and just tried some chords out, and found that they like the sound of these chords in that order. There's nothing inherently wrong with this approach, it just doesn't necessarily conform to standard music theory.
To use this understanding for melody writing, start with the set of notes above, and just do a bit of trial and error, see what sounds nice to you.
Note: On your last question, of whether you can sustitute Bb for Bdim. This is a common bit of Jazz theory called a tritone substitution. It's essentially playing a dominant 7th without the root note (e.g. Bb7 is Bb, D, F, Ab and Ddiminished is D, F, Ab). So a D diminished would replace Bb, and strongly lead you down to the key of Eb.
If you make it a diminished seventh, tho. It replaces the dominant 7th of one semitone lower than any of its notes. Ddim7 could be:
- A rootless D, leading to G.
- A rootless F, leading to Bb.
- A rootless Ab, leading to Db.
- A rootless Bb, leading to Eb
I can't, however, see it leading you back to a C chord. (Typically, a strong movement to C would include the leading note of the C major scale, B. For instance, G).
I would say it's a G mixolydian. I listened to the song, and the G and C both had strong tonality, although the G felt more like tonic, so it's the mode of C starting on G which would be mixolydian. The Bb chord is probably a result of the artist trying to give the song a minor feel, because it modulates to g minor, then promptly back into the G mixolydian.
I may also be completely wrong, because this song is fairly bluesy and pop-like, and there may be no established key. Or I may be overanalyzing it and it's something simple like Caleb said.
There is often the facility in a song to use the PARALLEL KEY. For instance, in C maj., there's C, Dm, Em, F, G, Am, Bo. In C min., there'll be Cm, Do, Eb, Fm, Gm, Ab, Bb. So any of this bank can and are used in a piece 'in C'. This then says that the piece in question could well be 'in C'. Thinking another way, with all but the G chord, it could be in F. The G could then be construed as the secondary dominant - dominant of the dominant - which is G pushing to the dominant of F, C.
I believe what is taking place is a momentary modulation utilizing 'common chord' technique... The progression begins in C with a V-ii movement (and since the ii chord Dm is common to key of F as a vi chord it can be used to pivot) the second chord now 'seen' as vi in key of F and moves to the predominant of F as vi-IV movement... the predominant of F (Bb) then moves to the dominant of F (C) or continuing as vi-IV-V and then continues with F (which is a common chord in both key of F and key of C and allows pivoting back to key of C) F is the I chord in F major (and provides a cadence movemnt V-I, but as the I chord is also the IV chord in C it can be used to pivot back to the Predominant in key of C) which then readily flows back to the V chord in C major.
I have used techniques like this quite often... It surprises the listener by beginning in one key and then modulating to another key and back again - and because it is 'common chord' modulation it is difficult to tell exactly where in the song the music is transitioning to another key.
It could, however, be C mixolydian as this is commonly used in jazz and blues style genres. But if it were this.. it should be v-ii-VII-I-IV (these are the scale degress of C mixolydian) and the G would be minor. The V could be an altered or borrowed chord, but it is more likely the technique of common chord modulation.
Reference the chart at
Linking to tab, especially for a pop song, it pretty useless for finding a "key" because the thing most likely to be informative about the "key" will be the melody.
Rather than identify a "key", identify the tonic first, then try to identify a mode.
Keep in mind that mode mixing, modulating to different keys, and changing the tonic are all very common in many different styles.
Transcription and analysis requests are supposed to be off topic, but of course no meaningful answer can be given without doing both, so I only looked at free online sheet music and listened only to the beginning of the song.
The tonic is clearly
G. The rest is a consideration of mode.
The melody starts on a
B♮ and phrases end pretty conspicuously on
G. That provides a general major tonal quality.
B♭ chords and melody tones like
F♮ can be considered borrowed chords or mode mixing.
G tonic and the melody working with both
B♭ above it there is a bluesy feel. An ambiguous, shift major/minor third above the tonic is a blues characteristic.
Do you really need to make claim about a key, either
G major or
G minor? Why? The sheet music doesn't even show a dominant chord. The chord progression repeats around a
C | G progression. That would be a plagal cadence which is something akin to modal harmony. You don't need to bring "key" into the analysis. This isn't Eine kleine Nachtmusik.
I think the chorus goes a long way to clarify things. There are noticeable ascents on the
G major triad along with a descent from
E. The final melody of the chorus is an elaboration of the
G major triad.
The list of chords alone would suggest a key signature of one flat.
The melody suggests
G mixolydian which would be within the major family of modes. Chord progressions like
C G and
G Dm also fit nicely with
G mixolydian folk style harmony.
The sheet music opts for notating in
G major with a key signature of one sharp and using accidentals to spell the borrowed chords and modal mixing.