The melody of this Pink Floyd song seems to be in the Dorian mode, but there is a G chord in the second half of the verse. How can it be determined whether the song is in Dorian or Aeolian?
The TL;DR version is: scroll down to the "Therefore ..." at the end.
But if you want the exhaustive (exhausting?) details ...
From the Department of Taking Things too Far
There is general agreement that the primary pitches are
C. So, here's a detailed look at the other pitches that occur in the song.
B: 00:21 - 00:24. Guitar lick.
B-something: 00:50 - 01:01. (implied) In neither the G5 power chord, nor in the vocal harmonies it accompanies, do I hear a clearly articulated
Bb; however, I hear the chord more easily as
Gm; possibly because
B: 00:29 - 00:30. Same as 00:21.
Ab: 01:38 - 01:40. To be really picky about figuring out the mode, one must acknowledge the A flat in the guitar.
B: 01:43 - 01:45. Same as 00:21.
Db: 01:48 - 01:51. A variation on 00:21.
Gb): 01:53 - 01:56. Another variation on 00:21 .
B: Passing notes in the guitar at 02:17 - 02:18 (ascending) and (maybe, but definitely not B-flat) 02:27 - 02:28.
B: 02:31 - 02:33. Guitar ascending passing tone.
B: 00:33 - 00:43. The topmost note of the rhythm guitar
B: 00:46 - 00:47. Passing tone.
B: 01:38 - 01:47. Same as 00:33 - 00:43.
B: 01:50 - 01:51. Same as 00:46 - 00:47.
B: 02:47 - 02:52. Keyboard
B: 02:56 - 03:01. Keyboard
Bb: 03:10 - 03:15. Keyboard
B: 03:14 - 03:15. Guitar (against Keyboard
This is essentially the same as the album version of part II, except for the clear modulation to
F from 01:24 - 01:43, which oscillates between
Bb chords (temporary
IV) before moving to a transitional
Bb chords occur during the guitar solo in the same context as the album version, part II, but more frequently. For example, 06:05 - 06:19.
Finally, during the guitar solo, at 04:43, there's a passing
It's easy to see why the song would be interpreted as Dorian: the primary note selection corresponds to that mode.
B predominates by far, so can be considered far more influential in determining the mode than
Bb. All other pitches (
Ab) are rare and clearly do not contribute to determining the mode. (Note that the
Db in part I, 01:48, is playing the role of
Db and not acting as the leading tone
This is not Dorian. To be truly modal, one would expect to hear far more of the
B to emphasize the modality. Further, it would occur in different contexts.
B only occurs when accompanied by
G. In a truly Dorian setting, we would hear, say,
B against the
F chords, or in more rhythmically or melodically accented positions. Further, the only times we hear
Bb, it's clearly intended as a chromatic alteration (part I, 01:53) or part of a modulation to
It's also not Tonal Minor. To be minor in the Tonal sense, there would have to be the presence of a leading tone; i.e.,
C#. This never occurs (see above regarding the
It's also not Modal Aeolian (natural minor). To be Aeolian,
Bb would be essential, and
B to be avoided.
The song is decidedly
D minor pentatonic, with lots of
E for color, and a fair number of
just to make things confusing also for color, but occurring through modal mixture via
D major, rather than as an indication a true Dorian.
The dorian and aeolian scales differ by 6th step, which is Bb in D aeolian or B in D dorian. The chords used in the song: Dm, G, F, C all consist of notes from the D dorian scale, which suggests dorian harmony. The note Bb does not appear in the song.
The vocal melody has ambitus of just a sixth (C–A), and doesn't get to B neither at the top nor at the bottom. The guitar solo consistently jumps over the 6th step. The resulting scale: D E F G A C could be called D-minor hexatonic.
However, as the note B clearly appears in the song, I think it's more accurate to say the song bases on dorian harmony with melody omitting the 6th step.
If you play D dorian scale over the recording, it agrees, though the B note introduces a color which is apparently purposely avoided in the original. If you play A aeolian, it sounds either wrong, or suggests an alteration of the original harmony.
I don’t remember the details of the chorus, but B natural is pretty prominent throughout the verse. For instance the first chord after the d minor i chord is a G major IV chord. It’s true that lots of professional transcriptions will still have a flat in the key signature, under the rule (which I think is a bad rule) that you should always use the nearest minor or major key signature, but the Bb is naturalized throughout the verse.
Again, maybe that changes for the chorus, in which case we would say that there’s some kind of modal shift there, but the majority of the song is in D Dorian, regardless of any key signatures.
This song contains both B and B&flat. Putting it not into any mode, but squarely into D minor. Many pieces in D minor will use both these notes - they're found in the melodic minor scale.
But in any case, as Laurence Payne states - a song doesn't have to choose one mode and stick to it. There may be some rules pertinent in music, but that's certainly not one of them!