Decoding the Music Theory Debate: What Key is It Really?

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Written By Gary Daws

Chief Music Officer

As music enthusiasts know, determining the key of a song is crucial to understanding the structure and chord progression. But what happens when there is disagreement over which key a song is in? A recent Facebook thread has ignited a lively debate among musicians on what key a certain chord belongs to. Let’s break down the discussion and explore the various opinions.

The Chord in Question

The chord in question is a B flat major seventh (BbMaj7), which is composed of Bb, D, F, and A. However, the exact key that this chord belongs to is up for debate.

Opinions on the Key

Several commenters have shared their thoughts on what key the chord belongs to, and each opinion is rooted in a different music theory concept. Here are the different arguments:

  1. Cb Major

Some people argued that the BbMaj7 chord belongs to the key of Cb Major. They base their argument on the fact that Bb is the seventh degree in the Cb Major scale. However, Cb Major is a rarely used key, as it has seven flats in its scale.

  1. B Major

Others suggest that the chord belongs to the key of B Major. They argue that the BbMaj7 chord is an A# chord in the key of B Major, and that it is the major seventh chord of the key.

  1. C Mixolydian

A few people suggested that the chord belongs to the C Mixolydian mode. In this mode, the chord progression would be C7-F-BbMaj7.

  1. Cb Ionian, Cb Lydian, or C Mixolydian

Others believe that the chord can belong to various modes in the key of Cb Major, including Cb Ionian, Cb Lydian, or C Mixolydian.

  1. C Dominant 7th

Some suggest that the chord is a C Dominant 7th chord, which is composed of C, E, G, and Bb. In this case, Bb is the dominant seventh in the key of C.

  1. Cb Mixolydian

One commenter argues that the chord belongs to the Cb Mixolydian mode, which would have a chord progression of Cb7-Fb-BbMaj7.

  1. Other Keys

Some suggested that the key depends on the context and the surrounding chords. For example, if the previous chord is an Ab, then the chord in question would be in the key of Eb.

So what is it really?

As you can see, there are clearly multiple opinions on what key the BbMaj7 chord belongs to. Each opinion is valid and based on different music theory concepts. Ultimately, the key depends on the context of the chord progression and the musical style. However, it is important to have a solid understanding of music theory concepts to make informed decisions about key and chord progressions.