# Expedition 003

### 1. System name
Fragment Antiphony

### 2. Pitch organization
Pitches are generated by integer powers of the golden ratio (φ ≈ 1.618) above a reference of 180 Hz. The system uses the continuous segment n = −1 to n = +6: approximately 111, 180, 291, 471, 762, 1234, 1996, 3230 Hz. The sequence spirals outward and never closes on any interval. Because the ratio is irrational, no two intervals in the set are ever exactly equal, and no transposition coincides with any other. Interval hierarchy is moderate — the reference pitch (n = 0) functions as a weak axis, not a tonic. Pitch flexibility is high: each performer may bend a pitch up to a full fifty cents without stepping onto a neighboring pitch in the set.

### 3. Rhythmic organization
Isochronous metric at approximately 50 beats per minute. The notated rhythmic cycle is enormous — a full cycle runs to approximately twenty-four minutes — but no single performance realizes a full cycle. Every performance is a short window onto the cycle, and the window never begins at the same point twice. Tempo is maintained but drifts during performance: strict pulse is maintained within any twelve-beat span, but across longer spans the conductor accelerates or decelerates without warning.

### 4. Formal structure
Through-composed narrative, but the narrative is a fragment: the performers enter mid-gesture and exit mid-gesture. Pieces are 45 seconds to 2 minutes long. The longer notated cycle proceeds through ten sections, and a typical performance traverses one or two of those sections, beginning and ending at whichever grid positions the conductor chooses. This produces a fragmentary quality — every performance feels like it was lifted out of a longer unheard work.

### 5. Texture and voicing
Antiphonal choirs — two groups of three to five voices each, physically separated (left and right sides of the performance space). The two choirs alternate phrases. Within each choir, voice independence is near zero: all voices move in strict parallel motion, each voice offset from the others by a fixed number of positions along the golden-ratio spiral. When choir A holds, choir B moves; when B holds, A moves. At no point do the two choirs sound simultaneously.

### 6. Ornament and inflection
Rhythmic-only. No pitch bending, no sliding, no vibrato — pitches are struck cleanly. Ornament is entirely rhythmic: each phrase is embellished with obligatory rhythmic subdivisions and accent patterns that do not affect the pitch sequence. A plain note is never sounded; every attack carries a micro-rhythmic figure around it.

### 7. Performance context
The system is didactic — performed by practitioners, for practitioners. Learning is through recorded references: students study recordings of fragments rather than being taught by a living teacher. There is no intended listener beyond the practitioners themselves, who perform the fragments to remain familiar with the larger notated cycle that none of them has ever heard in full. Silence is structural: the silence between the two choirs' alternations is as precisely timed as the sounded phrases.

### 8. Relationship to neighboring systems
Sits between Venetian polychoral music (two antiphonal groups, alternating) and Xenakis-era indeterminacy (irrational tuning, fragmentary form). Shares the antiphonal structure of Gabrieli and the irrational-ratio tuning of post-war modernism, but diverges from both by making the notated cycle so long that no performance completes it. The specific combination of `voice_count` high with `voice_independence` near zero is unusual: it is not a solo tradition, nor a polyphonic ensemble, but a doubled unison-in-parallel — two choirs moving as single organisms, alternating through a cycle too large for any one lifetime.

### 9. Audio specification

```json
{
  "duration_seconds": 75,
  "pitch_system": {
    "encoding": "ratio",
    "reference_hz": 180,
    "pitches": [0.618, 1.000, 1.618, 2.618, 4.236, 6.854, 11.090, 17.944],
    "octave_repeats": false
  },
  "rhythm_system": {
    "type": "metric",
    "tempo_bpm": 50,
    "beats_per_cycle": 12,
    "subdivisions_per_beat": 4,
    "accent_pattern": [1.0, 0.4, 0.6, 0.4, 0.5, 0.4, 0.8, 0.4, 0.6, 0.4, 0.5, 0.4]
  },
  "voices": [
    {"name": "choir_A_low", "timbre": "vocal_male_low", "pitch_indices": [1, 2, 3], "rhythm_role": "ostinato", "amplitude": 0.6, "spatial_position": [-0.85, 0.0], "active_sections": ["A_1", "A_2", "A_3"]},
    {"name": "choir_A_mid", "timbre": "vocal_female_high", "pitch_indices": [3, 4, 5], "rhythm_role": "ostinato", "amplitude": 0.55, "spatial_position": [-0.75, 0.1], "active_sections": ["A_1", "A_2", "A_3"]},
    {"name": "choir_A_high", "timbre": "vocal_female_high", "pitch_indices": [5, 6, 7], "rhythm_role": "ostinato", "amplitude": 0.5, "spatial_position": [-0.7, -0.1], "active_sections": ["A_1", "A_2", "A_3"]},
    {"name": "choir_B_low", "timbre": "vocal_male_low", "pitch_indices": [0, 1, 2], "rhythm_role": "ostinato", "amplitude": 0.6, "spatial_position": [0.85, 0.0], "active_sections": ["B_1", "B_2", "B_3"]},
    {"name": "choir_B_mid", "timbre": "vocal_female_high", "pitch_indices": [2, 3, 4], "rhythm_role": "ostinato", "amplitude": 0.55, "spatial_position": [0.75, 0.1], "active_sections": ["B_1", "B_2", "B_3"]},
    {"name": "choir_B_high", "timbre": "vocal_female_high", "pitch_indices": [4, 5, 6], "rhythm_role": "ostinato", "amplitude": 0.5, "spatial_position": [0.7, -0.1], "active_sections": ["B_1", "B_2", "B_3"]}
  ],
  "form": {
    "arc_type": "through_composed",
    "sections": [
      {"name": "A_1", "start_seconds": 0, "duration_seconds": 10, "character": "choir A — opening phrase of fragment"},
      {"name": "gap_1", "start_seconds": 10, "duration_seconds": 2, "character": "structural silence"},
      {"name": "B_1", "start_seconds": 12, "duration_seconds": 10, "character": "choir B answers, parallel spiral motion"},
      {"name": "gap_2", "start_seconds": 22, "duration_seconds": 2, "character": "structural silence"},
      {"name": "A_2", "start_seconds": 24, "duration_seconds": 12, "character": "choir A — extended phrase"},
      {"name": "gap_3", "start_seconds": 36, "duration_seconds": 2, "character": "structural silence"},
      {"name": "B_2", "start_seconds": 38, "duration_seconds": 12, "character": "choir B — extended answer"},
      {"name": "gap_4", "start_seconds": 50, "duration_seconds": 2, "character": "structural silence"},
      {"name": "A_3", "start_seconds": 52, "duration_seconds": 9, "character": "choir A — fragment closing"},
      {"name": "gap_5", "start_seconds": 61, "duration_seconds": 2, "character": "structural silence"},
      {"name": "B_3", "start_seconds": 63, "duration_seconds": 12, "character": "choir B — ends mid-phrase"}
    ]
  },
  "ornamentation": {
    "density": 0.87,
    "rule": "Each struck pitch carries a micro-rhythmic figure — a grace-beat either immediately before or after the main onset. No pitch bending."
  }
}
```

### 10. Field note
The space between the two choirs is where the music actually lives — each alternation is heard not as an answer but as evidence that the unheard full cycle continues somewhere beyond the room.