What this page is: A faithful standalone copy of the what-you-played.html that Claude generated ad hoc during a real MIDI harness session (2026-05-30 → 2026-06-01). The original lives at ~/Documents/midi-harness/what-you-played.html — this is that file, preserved here as a node artifact so visitors can see what Claude actually produces. No skill, no prompt line — Claude wrote chord cards + fingered keyboards from scratch every session.

What You Just Played

C → F → Cmaj13

C Major (arpeggiated)
I — played one note at a time: C, E, G

C4thumb (1)

E4middle (3)

G4pinky (5)

Root-position triad, right hand. The 1-3-5 hand shape is the home base — every triad in root position uses these same fingers.

F Major (arpeggiated)
IV — played one note at a time: F, A, C

F3thumb (1)

A3middle (3)

C4pinky (5)

Same 1-3-5 shape, shifted down to F. Notice C4 is shared with the C chord above — the common tone linking I and IV.

Cmaj13 ✦
the funky one — root, major 7th, 3rd, 13th

C3LH pinky (5)

B3RH thumb (1)

E4RH index (2)

A4RH pinky (5)

An open "spread" voicing: low root in the left hand, then B (major 7th), E (3rd), and A (13th) stacked wide in the right. No 5th at all — jazz voicings drop it because it adds nothing. The B a major 7th above the bass C is what gives it that shimmering, unresolved glow.

Why the last one sounds different

The two triads are pure and closed — every note within one hand span, nothing but 1-3-5. The Cmaj13 spreads the same C-major DNA across nearly two octaves and swaps the plain 5th for color tones (7th and 13th). Same key, same root, completely different atmosphere — that's basically the whole jazz-voicing trick in one chord.

Provenance: This chord card was generated by Claude in response to <played>C3 G3 C4 E4 x3 / F2 F3 A#3 D4 / G4</played> — 34 raw JSON lines on disk collapsed to 3 chord lines by the hook. The hook reads the whole events.jsonl, deletes it, clusters note-on/off pairs into chords, then emits the <played> block. Claude wrote the chord card, keyboard diagram, and finger annotations ad hoc — it's not a skill or a prompt instruction; Claude invents this format each session. See the diagram for the full data flow.