Generation

TECHNICAL_GUIDE.md

@@ -122,9 +122,9 @@ Measure durations, event onsets/durations, harmony offsets, span times, and pitc
 
 ### Shared Part Generation
 
-`parts.py` owns shared source validation, melody-copying, measure construction, rests, and solo slashes. `rhythm.py` loads snippets; `accompaniment.py` plans phrase cycles and realizes independent bass/upper voices or electric stabs. After guitar placement and continuation linking, `acoustic.py` combines generated bass/upper lanes into one notated voice. `melody.py` identifies long tied melody runs and splits them at harmony changes before guitar placement. `arrange/generate.py` supplies the existing seven-section song form; `practice/generate.py` supplies a single source pass. `pitch.py` resolves source instrument transposition and the shared written-octave convention. There is no generic twelve-key transposer or separate practice fretboard solver.
+`parts.py` owns shared source validation, melody-copying, measure construction, rests, and solo slashes. `rhythm.py` loads snippets; `accompaniment.py` plans phrase cycles and realizes independent bass/upper voices or electric stabs. Before guitar placement, `acoustic.py` shortens generated bass/upper attacks so they cannot overlap; afterward it combines them into one notated voice. `melody.py` identifies long tied melody runs and splits them at harmony changes before guitar placement. `arrange/generate.py` supplies the existing seven-section song form; `practice/generate.py` supplies a single source pass. `pitch.py` resolves source instrument transposition and the shared written-octave convention. There is no generic twelve-key transposer or separate practice fretboard solver.
 
-Acoustic consolidation preserves the exact sounding-note timeline and TAB assignments. It combines simultaneous tones, splits sustains at intervening attacks/releases, and ties only fragments of the same sounding note or existing tie chain. Repeated pitches remain fresh attacks. Rests represent complete silence, with one measure rest for a silent full bar. Independent stem directions and old beam groups are removed; standard single-voice engraving supplies shared stems and automatic beams. Binary durations that require multiple written values become ordinary tied notes rather than artificial tuplets. Exact nonbinary timing retains the model's rational time modifications. This pass leaves authored voices and solo slashes unchanged and runs entirely at build time.
+Generated accompaniment has no ties. Acoustic attacks release at the earliest of their planned end, the next combined bass/upper attack, or the barline. Simultaneous bass/upper attacks use the shorter planned duration for the entire grip. If a binary duration would need ties, it shortens to the longest conventional single note that fits, followed by silence; no extra attack or artificial tuplet is introduced. Rhythm-snippet continuations are silent, and the planner does not count them as acoustic coverage. After placement, consolidation preserves the prepared timing and TAB assignments, combines simultaneous tones under one stem, and writes rests only for complete silence. A silent full bar has one measure rest. Old lane stem directions and beam groups are removed in favor of single-voice engraving. Authored melody ties, solo slashes, and electric melody harmonization remain separate from this build-time accompaniment policy.
 
 Practice acoustic accompaniment is derived from structured harmony roots, kinds, degrees, inversions, and slash basses using the same generation rules as songs. A missing harmony or N.C. produces rests, not guessed chords. Electric retains the melody's register and spelling while adding playable chords to long notes. Vocal retains authored notes and receives scat lyrics. Song vocal lyrics are unchanged. Practice optional-turnaround harmonies are played once, without creating extra sections.
 
@@ -138,11 +138,15 @@ All three parts, for both songs and practice, use octave-transposing notation: w
 
 `guitar.py` searches standard tuning E2 A2 D3 G3 B3 E4, frets 0-20 inclusive, with at most four frets between the lowest and highest positions, including fret 0. Open strings participate in span validation and proximity scoring: 0/2/3 and 0/4 are valid, while 0/5 and 0/11/12 are not. Exact melody tones are never dropped or replaced. Simultaneous tones occupy distinct strings, and sustained/tied tones retain their assignments. Acoustic grips use one bass on string 5 or 6 and two or three consecutive strings within 2-4, with zero or one unused string between bass and upper voices. Both rhythmic voices must fit one complete grip, even when only one attacks. Bass alternates root and chord fifth, restarting at harmony/section changes; explicit basses/inversions remain fixed. A fifth-bass choice falls back to the root if it cannot preserve chord identity and the held strings.
 
-Electric chord blocks use strings 1-3 or 1-4, including string 1. Rootless voicings and octave doublings are allowed; the third or suspension, sixth/seventh, alterations, and named extensions remain required. An unaltered fifth in extended chords and unaltered intermediate ninth/eleventh extensions may be omitted. Melody notes can lie below added chord tones, including non-chord melody pitches that must remain unchanged.
+Electric chord blocks use strings 1-3 or 1-4, including string 1. Rootless voicings and octave doublings are allowed as fallbacks; the third or suspension, sixth/seventh, alterations, and named extensions remain required. An unaltered fifth in extended chords and unaltered intermediate ninth/eleventh extensions may be omitted. Exact melody pitches, including non-chord tones, remain unchanged. Root preference never restores a degree explicitly subtracted from the harmony.
 
 `melody.py` treats the full tied duration as one note when testing whether it exceeds one quarter-note beat. Qualifying notes receive a chord at their initial attack and at each subsequent changed harmony, even if a resulting fragment is less than one beat. Changed harmonies break ties and reattack the melody; repeated identical harmonies do not. N.C. releases the added voices while preserving the melody's sustain. Added tones through unchanged harmony retain their own ties. The quarter-note cap on electric stabs does not apply to these melody chords. If no valid chord fits, the exact melody remains with a diagnostic; it is not octave-wrapped or omitted.
 
-Placement minimizes total movement of fret/string position centers, then fret span and omitted optional degrees, with deterministic ties. All three calculations include open strings. Independent attacks use an exact small-grid distance transform; when notes sustain across attacks the search retains actual occupied strings. There is no finger assignment, barre logic, or predefined chord-shape dictionary. These are proximity and fretboard-feasibility constraints, not a guarantee of comfortable fingering. Nonstandard tuning, capos, microtonal frets, and unplayable passages fail with source/part/event context; there is no slash fallback for a failed chord. Existing assets remain untouched after failure.
+Placement uses the ordered `VoicingCost` components: electric string shortfall from four, melody covered, number of tones above the melody, missing root, physical effort, and missing optional pitch classes. These costs accumulate over the whole passage, so movement cannot outweigh the earlier musical priorities. Melody height compares sounding pitch; unison doubling does not cover it. Electric accompaniment uses the same ranking without the melody-height terms. Acoustic does not receive electric fullness/root penalties: a simpler three-note grip can beat a more awkward four-note grip while satisfying its hard harmonic requirements.
+
+Physical effort is `movement + 2 * highest_fret + fret_span` for electric and exact melody placement, and `movement + 2 * highest_fret + 3 * fret_span + 2 * (distinct_frets - 1)` for acoustic. Movement is the Manhattan distance between doubled fret/string position centers. Open strings count in every fret measurement. Simultaneous bass/upper attacks are scored once as a full grip; pure tie continuations add no fresh shape or movement cost. Lower positions receive a continuous preference with no comfort threshold or automatic octave fitting. Candidate pruning and the exact small-grid distance transform share this ranking; held notes keep their occupied strings and all compatible candidate states. Stable position ordering resolves equal costs.
+
+There is no finger assignment, barre logic, or predefined chord-shape dictionary. These are proximity and fretboard-feasibility constraints, not a guarantee of comfortable fingering. Nonstandard tuning, capos, microtonal frets, and unplayable passages fail with source/part/event context; there is no slash fallback for a failed chord. Existing assets remain untouched after failure.
 
 ### Practice Scat