What's the theory behind using a B major chord in Bb major?

Question

If you're in Bb major, how can you use a Bb major chord and a B major chord?

Bohemian rhapsody is a good example.

|B Bb A Bb|B Bb A Bb|

http://www.queensongs.info/song-analysis/songwriting-analyses/no-synth-era/a-night-at-the-opera/bohemian-rhapsody

http://www.e-chords.com/chords/queen/bohemian-rhapsody

Answer 1

Jazz people call it sideslipping and it's a way of reinforcing your primary chord. Your primary chord is Bb, so if you temporary move up (or down) a half-step and back, it tends to reinforce the sound of Bb as "home base".

Answer 2

When playing in a key, not every single note/chord played needs to be in a key. The analysis you link is as follows:

Bb:
|B Bb A Bb|B Bb A Bb|
|  I    - |  -    - |

What it mean though is simple. In this section we're perceiving the Bb chord as "tonic"and the B and A chords really don't function in a traditional sense and are more for ornamentation. There's this idea of neighbor tones in music where you play the note above or below and go back to the original note and it's an acceptable way to add tones to harmony that you typically wouldn't. I would go as far as to call these chords chromatic neighboring chords since that's really what's going on.

It's a really good ornamentation because of how it goes with the unsteadiness of the whole section and make you feel like you are going somewhere when in actuality you are not.

Answer 3

This is the 'easy come, easy go' part, right?

Firstly, in a rock and pop music in general, taking the same chord shape and moving it around is a common device. Think of the F-C-G-D-A (all major) flourish at the end of the Time Warp chorus, or the all minor chord progression Bm-F#m-Am-Em in Inner City's Goodlife.

Obviously doing this often takes you outside the 7 notes of a key. Why is that not a problem? Well, it turns out that our ear (or at least, many people's!) are quite happy to hear the same chord shape shifting up and down in pitch. It's quite a dramatic effect, as 'the whole thing is moving' - and it catches the ear much more than just changing chords within a scale - which of course is what is intended. Also, rock music comes partly from (modal) folk and blues traditions where listeners are less likely to 'expect' to hear music stick to the seven notes of a major or minor key, which is another reason that it's fine to do this kind of thing.

Having said that, a lot of pop and rock music does genuinely follow the 'common practice'-type harmony of sticking to a major or minor scale, and the clever thing in Bohemian Rhapsody is that it does set up an expectation that it's moving towards a straightforward major key tonality, and then that |B Bb A Bb|B Bb A Bb| section catches you off guard - when I listen to it I feel like I am physically moving up and down with the pseudo-melodic chord motions.

There are other ways that out-of-the-key chords can come into play - when setting up a modulation to another key, or when you're 'borrowing' a chord from a related key. But I don't think these are good descriptions of what's happening here, although if you wanted, you could think of B-Bb-A-Bb as three semitone modulations in a row.

Answer 4

Fellow music theory student here, so take my answer with a grain of salt:

Not all notes of a song has to be diatonic; in fact, it sounds quite boring if every note in the piece is diatonic. In this case, I think the B chord is used as a neighbor tone, one of the ways to make the music more interesting.

Answer 5

Understanding these more complex kinds of musical phenomena depends ultimately on one's own interpretation. The analysis in the first link you've provided calls Bb the tonic chord during the entirety of the chromatic neighbor motion in question. My view of this passage, however, is that Eb is in fact functioning as a local tonic, with Bb as its dominant.

Immediately following this progression, a major triad built upon Eb is heard as the downbeat of the measure containing the lyric "Anyway the wind blows." This chord is emphasized additionally by an increase in orchestration. To support my interpretation as Eb as a local tonic are the three chords addressed in your question. The B-major chord (more appropriately spelled as Cb-major in this context) in combination with Bb-major and A-major resemble a familiar scale degree motion surrounding dominant scale degrees, i.e. b6-5-#4. Chromatic neighbour tones such as these commonly serve to emphasize the dominant scale degree, 5. A vertical example of this are augmented-sixth chords, which contain b6 and #4; these two chord members typically both resolve to scale degree 5. Horizontally it is common to find this kind of motion in one voice. Queen, however, have embellished this melodic idea by filling it out with triads, making for quite an interesting punctuation.

The Cb-B-A-B (b6-5-#4-5) root motion of the chords resolving to a downbeat Eb (sd 1) to me is unmistakably pointing to Eb as the local tonic. Bb follows shortly afterwards, however, reestablishing itself as the more global tonic in the section of the song.

Answer 6

The big thing here is to understand that you can use any notes you want as long as you do it in a way that will strengthen or weaken your tonality of any given key. There are no set "rules", but understand that by introducing non-diatonic notes, it will have an effect on the tonality of your piece/phrase/bar or on how you are modulating to a new key.

EDIT: I should note that obviously the above paragraph is a very, very, simple way of putting it.

Michael Martinez seems to have hit it right on point; the composer is using that "sidestepping" to enforce Bb in a harmonically-rhythmically ordered fashion (of course the harmonic rhythm is also helping to enforce Bb in this example).

Try listening to some very late romantic or modern classical music. Check out Rachmaninov's famous C#m prelude that contains parallel fourths falling chromatically downwards to the dominant note in the "middle" section of the piece (I don't remember the structure of the piece).

Answer 7

It could also be used as a chromatic device to the next chord Bb --> B --> C. The same way non chord notes are sometimes chromatically to go the next chord / note.