Exploring the Differences Between BIII and III Chords in Music Theory
Understanding the Basics of Chords in the Major Scale:
In the context of music theory, the III chord and the BIII chord hold unique positions within the structure of a major scale. The III chord, commonly known as the submediant chord, is built from the third degree of the major scale and tends to function as a harmonic pivot point. However, it falls on a minor triad when the scale is in natural form.
The Nature of the III Chord
The III chord in the key of C major (C, D, E, F, G, A, B) is E minor (E, G, B). This chord is typically used to create a sense of resolution or to change the key temporarily by modulating to a distant key. Its minor quality provides a somewhat dark or brooding atmosphere in the music, making it a staple in numerous classical and modern compositions.
Introducing the BIII Chord: An Altered State of the III Chord
The BIII chord, on the other hand, is derived by altering the III chord. It is formed by lowering the third of the III chord by a semitone, shifting it from E to Eb (E flat). This gives the BIII chord a major triad formation (B, D, F), making it function differently in the harmonic progression. This alteration creates an 'altered' state and distinct sound.
Altered Chord Characteristics
The key feature of the BIII chord is that it introduces altered tones into the key, often used to create tension and then provide resolution. Altered chords typically modify the natural triad to include sharp or flat notes that are outside the key. In the case of the BIII chord, the alteration of the third allows it to function more prominently in the chord progression, often serving as a V7 chord in chords like B7, E7, etc., due to its resemblance to a dominant seventh chord, which resolves well to the tonic (C major).
Implications in Harmonic Progression
When using the BIII chord in a harmonic progression, the altered quality often creates a sense of harmonic tension that can be resolved in various ways. By resolving a BIII chord to the IV chord (F major in the key of C), the music can take on a different character with smoother resolution. This makes the BIII chord particularly useful in building and resolving tension in complex musical arrangements. It can also serve as a stopover chord in key changes, contributing to the harmonic journey of a piece of music.
Practical Applications of BIII and III Chords
Beyond just theoretical analysis, the practical application of these chords is significant. Composers and songwriters often use altered chords like the BIII to add color and unexpected twists in their music. For instance, in a blues progression, the BIII can provide a contrasting color next to the expected III chord. Similarly, in jazz and pop music, these chords are used to embellish traditional chord progressions and explore new soundscapes.
Conclusion
The difference between the BIII and III chords lies in the altered state of the former. While the III chord remains a minor triad, the BIII chord’s altered third transforms it into a major triad, offering a different harmonic function and sound. Both chords are valuable tools in the music theory arsenal, each contributing unique qualities to harmonic progressions and musical textures.
Understanding the distinction between these chords can significantly enhance one's ability to analyze and compose music, providing deeper insight into the complex interplay of notes and chords in different musical styles.