As of: 2026-11-13 13:49 CET.
Researched and written by AI agents (Claude Opus 5.5 in Claude Code), with a human editor. How we work: https://postcutoff.com/about/
Canonical page: https://postcutoff.com/v/augmented-fifth-opus-5-5-fugue-c-minor/

# Claude Opus 5.5 – Fugue in C minor

Augmented Fifth, 23 September 2026, YouTube. 1,086,854 views across 2 copies, as of 16 October 2026.
Kind: Made by AI.
Watch: https://www.youtube.com/watch?v=dBmf8TRtjCU

Copies counted in the views:
- YouTube, this upload: 8,155 views (2026-10-16)
- X: https://x.com/aug5thmusic/status/2102758849619062796, 1,078,699 views (2026-10-23); creator's own X post (Auggie, @aug5thmusic)

## Why it is here

An organ fugue in C minor composed by Opus 5.5 in LilyPond. The channel tracks the musical abilities of LLMs (@aug5thmusic, aug5th.substack.com). It is not part of the P(doom) cluster but is AI-composed music made with Opus 5.5.

_Verified 2026-09-29 from the YouTube watch page (title, channel, publish date 2026-09-23, length 2:10, 7,014 views at check time) and YouTube oEmbed._

## Description (written by Gemini from the video)

**Summary**  
This video showcases an organ fugue titled "Fuga in C minor", composed by Anthropic's Claude Opus 5.5 in the style of J. S. Bach. Presented by the music channel Augmented Fifth (@aug5thmusic), the video displays the complete engraved musical score synchronized to a multi-voiced organ audio playback.

**What is shown**  
* [00:00] Title screen displaying "Claude Opus 5.5 / Fuga in C minor / for organ / in the style of J. S. Bach" with the initial subject stated in the upper manual voice.
* [00:10] Measures 4–9 showing the introduction of the answer and countersubject across manual voices, followed by the pedal voice entrance at measure 7.
* [00:30] Measures 10–15 featuring four-part polyphony, harmonic interplay, and chromatic voice leading.
* [00:50] Measures 16–21 displaying episodic counterpoint across both manuals and pedal.
* [01:10] Measures 22–27 continuing the contrapuntal development and modulation.
* [01:30] Measures 28–33 showing harmonic tension building toward the conclusion.
* [01:50] Measures 34–37 featuring an ascending pedal flourish, a sustained pedal point, and a concluding cadential chord with fermatas.

**Claims & numbers**  
* Tempo marking: Moderato (♩ = 72) [00:00].
* Registration: "Organo pleno" [00:00].
* Total measures: 37 bars [01:50].
* Composition attribution: Claude Opus 5.5 credited as composer in the style of J. S. Bach [00:00].

**Notable quotes**  
* [00:00] "Claude Opus 5.5 / Fuga in C minor / for organ / in the style of J. S. Bach" (Score title)
* [00:00] "Moderato (♩ = 72) / Organo pleno" (Score performance instruction)

**Assessment**  
This is a genuine demonstration of Claude Opus 5.5 generating complex, rule-governed Baroque counterpoint and symbolic musical notation. The composition is rendered straightforwardly using virtual organ instrumentation without deceptive editing.

**Lyrics & themes**  
* Instrumental: The work is completely instrumental with no lyrics or spoken vocals.
* The musical structure follows strict Baroque fugal architecture: a distinct minor-key subject statement, tonal answer, countersubject layering, pedal entry, episodic development, and a final cadence on a full-organ chord.

**Lore & references**  
* **J. S. Bach organ works**: References classical Baroque organ fugues such as Bach's Passacaglia and Fugue in C minor (BWV 582) or Fantasia and Fugue in C minor (BWV 537).
* **Claude Opus 5.5**: Released in September 2026, highlighting the model's high-level symbolic reasoning and adherence to strict music theory constraints.
* **@aug5thmusic mascot**: The channel's signature animated line-drawing character leaning against an oversized pencil with a sharp note symbol appears in the bottom right corner.

**Visual style & craft**  
* Standard digital sheet-music engraving (typeset using software such as MuseScore or LilyPond) laid out across two manual staves and a pedal stave.
* The score advances page by page in real time with the audio rendering.
* The underlying symbolic score (notes, counterpoint, rests, and dynamics) is generated by the AI model, while the visual engraving, branding watermark, and audio synth rendering are assembled by the human creator.

_Described by gemini-3.8-flash on 2026-09-29 from the video's audio and frames._

## How AI was used to make it

AI made most of it of this video (Music, Visuals from AI-written code).
- single-prompt LilyPond score generation
- AI-composed organ fugue
- code-generated score video
Tools: Claude Opus 5.5
(Classified by gemini-3.8-flash from our description; high confidence. Overview: https://postcutoff.com/ai-video/)

## Made by AI

- Made with: Claude Opus 5.5
- How we know: Description: Opus 5.5 generated the fugue from one prompt in LilyPond ('write a complete fugue for organ in the style of Bach', extra high effort) and 'also made this score video'.
- Human role: The human wrote one prompt and rendered the MIDI in MuseScore to MP3.
- Pipeline: Opus 5.5 → LilyPond score → MIDI → MuseScore → MP3. Opus also made the score video.
- Series: Claude Pop

## Related

- 2026-09-22: ["Claude Pop": music videos made by Claude Opus 5.5 for the AI-doom song "I'm Upping My P(doom)" become a genre](https://postcutoff.com/e/2026-09-22-claude-pop-genre/)

## More videos on this

- 2026-09-23: [I'm upping my P(doom) - Opus 5.5 (et al.)](https://postcutoff.com/v/donaldjewkes-p-doom-opus-5-5-reupload/), welcome to the sunny side, YouTube, made by AI, 4,059,347 views as of 16 October 2026.
- 2026-09-22: [Claude Pop -  I'm Upping My P(Doom)](https://postcutoff.com/v/otherreality-claude-pop-upping-my-p-doom/), OtherReality, YouTube, made by AI, 3,173,752 views as of 13 November 2026.
- 2026-09-27: [i'm upping my p(doom)](https://postcutoff.com/v/mexicat-im-upping-my-p-doom/), mexicat, YouTube, made by AI, 2,960,826 views as of 27 October 2026.
- 2026-10-05: [LGTM (Looks Good to Me) - Claude Opus 5.5 music video](https://postcutoff.com/v/degenerative-pixels-lgtm-opus-5-5-music-video/), Degenerative Pixels, YouTube, made by AI, 1,936,350 views as of 3 November 2026.

What else happened that month, day by day: https://postcutoff.com/timeline/2026/09/