Anchor Structures Finder

Anchor Structures and Adorning Notes

Originally proposed by Damian J. Blättler as a method for analysing the Parisian modernist repertoire of composers like Ravel and Debussy, anchor structures are defined as

the vertical-domain component of a novel chord that allows for its participation in tonal progression.

To put it simply, while the Parisian modernist composers have used a plethora of wacky unheard-of chords and voicings, certain passages exhibit sonorities that feel almost tonal. It seems as if they are siblings of chords with traditional tonal functions, signified by the anchor structures within the voicing, and enhanced by additional adorning tones that colour the harmony. Blättler outlined some observations about which anchor structures and adorning tones are permissible to preserve the tonal resemblance. They are as follows:

1. First-order anchor structures are two-note patterns, including 5ths, minor and major 7ths.
2. Second-order anchor structures are three-note patterns, including
   • consonant triads in inversion,
   • seventh chords in inversion with the omission of either the chordal third or fifth,
   • the diminished triad and its inversions.
3. When there are multiple anchor structures in the voicing, the general tendency is that
   • Structures closer to the bass is more prevalent than those above.
   • Two-note structures trump over second-order structures.
4. Minor 2nd and minor 9th etc. may introduce too much roughness that counters against hearing a sonorous composite chord.
   • An exception is the minor 9th above the bass of a chord with a two-note anchor structure.
5. Consecutive whole steps may blur the distinction between chords and scales.
6. No adjacent tones are more than an octave apart.
7. Ultimately, it all depends on the context.

I believe these are the gist of Blättler’s idea. For more detailed and nuanced description with examples, please refer to the original paper.

The Tool

I spent one night creating this simple web tool that can help analyse any chord voicing within 3 octaves, and identify anchor structures as well as potential pitfalls.

For simplicity, the bass note is fixed to C. You can add/remove toppings by clicking on the vertical keyboard, and all identified structures will be shown on the right side, in the same row as the root note of the structure.

First-order structures are green, second-order structures are blue, while potential rule violations are coloured red. Hover above them will show you every note in the structure, as well as the chord they stand in for.

I didn’t add an exception for bass-9th structures, nor did I enforce rule 6. So please use your own judgment, cheers.

References

• Blättler, Damian J. 2017. “A Voicing-Based Model for Additive Harmony.” Music Theory Online 23(3): 1–28.
• Blättler, Damian J. 2013. “A Voicing-Centered Approach to Additive Harmony in Music in France, 1889-1940.” PhD diss., Yale University.