fix(library): tuning filter answers for your instrument, not always guitar

The library indexed exactly one tuning per song, chosen guitar-first (lead >
rhythm > combo, bass only as a last resort), and nothing consulted the
player's instrument. A bassist filtering by tuning was shown the guitar
chart's tuning, so playlists built by tuning contained songs needing a
retune. Reported by a tester building bass practice sets; Covet "Shibuya" is
the clean case, with a custom guitar tuning over a standard bass chart.

Indexes each arrangement role's own tuning and makes the facet, filter, sort
and labels answer for one perspective. `guitar-lead` reads the original
unprefixed columns and adds no payload keys, so the default response is
unchanged. The same defect existed inside guitar -- lead and rhythm charts
can disagree -- so perspective is three-valued (guitar-lead, guitar-rhythm,
bass) driven by one PERSPECTIVES table rather than parallel column families.

Songs with no chart for the perspective fall back to the song-level tuning
rather than vanishing (18 of 59 packs in the test library have no bass
chart), but the fallback is marked inferred in the facet counts and on the
row instead of being silently coalesced. "Only real charts" reuses the
existing `arrangements_has` filter rather than adding one.

Bass-specific handling, from measured content:
- Bass tuning arrays are padded to six entries; charts never reference
  string index 4 or 5. Truncated to four before naming and grouping.
- Grouping uses a canonical open-pitch key, so [-2,0,0,0] and
  [-2,0,0,0,0,0] are one facet row instead of two.
- Offsets above +1 semitone are refused a name. Bassists tune down, near
  never up; one pack ships [5,5,5,5,4,4] (A-D-G-C, unplayable, and its own
  notes sit in the song's real key under standard tuning). Naming that
  would send a player to retune to a tuning that does not exist.

Rhythm deliberately does not truncate -- padding is a bass finding, and
cutting a seven-string array would invent a tuning the chart lacks.

Adds an opt-in `tuning_match=playable` mode alongside exact match: a chart is
offered when your lowest open pitch is at or below its lowest open pitch, so
a five-string bass covers four-string standard and drop-D with no retune.
Open strings only -- note range is not indexed and the scan stays
manifest-only -- so it fails conservative: unknown low pitch is excluded, and
the upper bound is unchecked and documented rather than guessed.

Existing installs would otherwise never populate: the tree-signature fast
path reports "unchanged" forever on a settled library. Rows with NULL marker
columns re-extract, and the fast path is disabled until that backfill
converges (writes use '' rather than NULL, so it self-clears).

Co-Authored-By: Claude Opus 4.8 (1M context) <noreply@anthropic.com>
Claude-Session: https://claude.ai/code/session_01SFDokqh2H6mEjk1Kgbi6JW
Signed-off-by: ChrisBeWithYou <christian.a.cowan@gmail.com>

static/js/library.js

@@ -410,6 +410,51 @@ function _applyLibraryProviderToParams(params) {
     return params;
 }
 
+// ── Instrument-aware tuning (the bass-player tuning-filter report) ───────────
+// A song's bass chart is often tuned differently from its guitar chart, so the
+// tuning facet, the `tunings` filter, the tuning sort and the row's tuning
+// badge must all speak for the instrument the player actually plays. Read the
+// host's working-tuning capability (the live selection, seeded from
+// /api/settings at boot) rather than adding another settings fetch; hosts
+// without the capability keep the guitar behaviour.
+const _LIB_PERSPECTIVES = ['guitar-lead', 'guitar-rhythm', 'bass'];
+let _libSettingsProfile = '';
+
+export function _setLibraryProfile(profileId) {
+    _libSettingsProfile = _LIB_PERSPECTIVES.includes(profileId) ? profileId : '';
+}
+
+export function _libraryInstrument() {
+    // The PROFILE is the only three-valued source (lead / rhythm / bass); the
+    // working-tuning capability knows guitar-vs-bass but not lead-vs-rhythm,
+    // so it is only the fallback.
+    if (_libSettingsProfile) return _libSettingsProfile;
+    try {
+        const wt = window.feedBack?.workingTuning;
+        if (wt && typeof wt.get === 'function') {
+            const cur = wt.get();
+            if (cur?.instrument === 'bass') return 'bass';
+        }
+    } catch { /* capability absent/erroring — lead guitar is the safe default */ }
+    return 'guitar-lead';
+}
+
+export function _libraryInstrumentLabel() {
+    const p = _libraryInstrument();
+    return p === 'bass' ? 'bass' : p === 'guitar-rhythm' ? 'rhythm' : 'lead';
+}
+
+// The tuning a row should SHOW: the bass chart's for a bass player, falling
+// back to the song (guitar-derived) tuning when the song has no bass
+// arrangement — the common case, not an edge path.
+function _rowTuningRaw(song) {
+    const p = _libraryInstrument();
+    const field = p === 'bass' ? 'bass_tuning_name'
+        : p === 'guitar-rhythm' ? 'rhythm_tuning_name' : '';
+    if (field && song[field]) return song[field];
+    return song.tuning || song.tuning_name || '';
+}
+
 export function _resetLibraryProviderViewState() {
     L.libEpoch++;
     L.currentPage = 0;
@@ -768,6 +813,8 @@ export function _applyLibFiltersToParams(params) {
     if (_libFilters.stemsLacks.length) params.set('stems_lacks', _libFilters.stemsLacks.join(','));
     if (_libFilters.lyrics !== null) params.set('has_lyrics', String(_libFilters.lyrics));
     if (_libFilters.tunings.length) params.set('tunings', _libFilters.tunings.join(','));
+    // Which instrument's tuning the `tunings` filter + the tuning sort read.
+    if (_libraryInstrument() !== 'guitar-lead') params.set('instrument', _libraryInstrument());
     return params;
 }
 
@@ -851,6 +898,7 @@ async function _renderTuningList() {
         c.innerHTML = '<div class="text-xs text-gray-500 px-2">Loading...</div>';
         try {
             const params = _applyLibraryProviderToParams(new URLSearchParams());
+            params.set('instrument', _libraryInstrument());
             const resp = await fetch(`/api/library/tuning-names?${params}`);
             if (!resp.ok) throw new Error(`HTTP ${resp.status}`);
             const data = await resp.json();
@@ -869,6 +917,11 @@ async function _renderTuningList() {
             fetchError = e.message || 'request failed';
         }
     }
+    // NAME the perspective: silent instrument-following is the original bug in
+    // a new place — the user must be able to see which instrument these
+    // tunings describe.
+    const labelEl = document.getElementById('filter-tunings-label');
+    if (labelEl) labelEl.textContent = `Tuning (${_libraryInstrumentLabel()})`;
     c.innerHTML = '';
     if (fetchError) {
         c.innerHTML = `<div class="text-xs text-red-400 px-2">Failed to load tunings (${esc(fetchError)}). Reopen the drawer to retry.</div>`;
@@ -894,10 +947,17 @@ async function _renderTuningList() {
         const checked = _libFilters.tunings.includes(val);
         const row = document.createElement('label');
         row.className = 'tuning-row';
+        // Be honest about the fallback: songs with no bass arrangement borrow
+        // the guitar chart's tuning, and that must be visible rather than
+        // presented as a measured bass tuning.
+        const inferred = t.inferred_count || 0;
+        if (inferred) {
+            row.title = `${inferred} of ${t.count} inferred from the guitar chart (no bass arrangement)`;
+        }
         row.innerHTML =
             `<input type="checkbox" ${checked ? 'checked' : ''} class="rounded border-gray-600 bg-dark-700 text-accent">` +
             `<span class="flex-1">${esc(label)}</span>` +
-            `<span class="tuning-count">${t.count}</span>`;
+            `<span class="tuning-count">${t.count}${inferred ? ` (${inferred}~)` : ''}</span>`;
         const cb = row.querySelector('input');
         cb.onchange = () => {
             const i = _libFilters.tunings.indexOf(val);
@@ -1244,6 +1304,10 @@ export function renderGridCards(songs, containerId = 'lib-grid', mode = 'replace
         const duration = song.duration ? formatTime(song.duration) : '';
         const tuningRaw = song.tuning || song.tuning_name || '';
         const tuning = displayTuningName(tuningRaw);
+        // The BADGE follows the player's instrument; `tuning` above stays the
+        // song's guitar-derived tuning because the retune action below rewrites
+        // the chart to E Standard and must not key on the bass part.
+        const tuningBadge = displayTuningName(_rowTuningRaw(song));
         const artUrl = _librarySongArtUrl(song, providerId);
         const isLocalProvider = _isLocalLibraryProvider(providerId);
         const isSloppak = song.format === 'sloppak';
@@ -1299,7 +1363,7 @@ export function renderGridCards(songs, containerId = 'lib-grid', mode = 'replace
                 </div>
                 <div class="flex items-center flex-wrap gap-1.5 mt-3 text-xs">
                     ${(() => { const _nm = _getArrangementNamingMode(); return (song.arrangements || []).map(a => _arrangementBadgeHtml(a, _nm)).join(''); })()}
-                    ${tuning ? `<span class="px-1.5 py-0.5 rounded ${tuning === 'E Standard' ? 'bg-green-900/30 text-green-400' : 'bg-yellow-900/30 text-yellow-400'}">${esc(tuning)}</span>` : ''}
+                    ${tuningBadge ? `<span class="px-1.5 py-0.5 rounded ${tuningBadge === 'E Standard' ? 'bg-green-900/30 text-green-400' : 'bg-yellow-900/30 text-yellow-400'}">${esc(tuningBadge)}</span>` : ''}
                     ${song.has_lyrics ? `<span class="px-1.5 py-0.5 bg-purple-900/30 rounded text-purple-300">Lyrics</span>` : ''}
                     ${song.user_difficulty != null ? `<span class="px-1.5 py-0.5 bg-blue-900/30 rounded text-blue-300" title="Your difficulty rating">◆${esc(song.user_difficulty)}</span>` : ''}
                     ${duration ? `<span class="text-gray-600">${duration}</span>` : ''}
@@ -1470,6 +1534,9 @@ export async function renderTreeInto(containerId, countId, stats, letter, q, fav
                 const duration = song.duration ? formatTime(song.duration) : '';
                 const tuningRaw = song.tuning || song.tuning_name || '';
                 const tuning = displayTuningName(tuningRaw);
+                // Badge follows the player's instrument; the retune action below
+                // keeps operating on the song's guitar-derived tuning.
+                const tuningBadge = displayTuningName(_rowTuningRaw(song));
                 const isLocalProvider = _isLocalLibraryProvider(providerId);
                 const isSloppak = song.format === 'sloppak';
                 const stdRetune = isLocalProvider && localFilename && !isSloppak && tuningRaw && !song.has_estd &&
@@ -1496,8 +1563,8 @@ export async function renderTreeInto(containerId, countId, stats, letter, q, fav
                 { const _nm = _getArrangementNamingMode();
                   for (const arrangement of (song.arrangements || []))
                       html += _arrangementBadgeHtml(arrangement, _nm); }
-                if (tuning)
-                    html += `<span class="px-1.5 py-0.5 rounded ${tuning === 'E Standard' ? 'bg-green-900/30 text-green-400' : 'bg-yellow-900/30 text-yellow-400'}">${esc(tuning)}</span>`;
+                if (tuningBadge)
+                    html += `<span class="px-1.5 py-0.5 rounded ${tuningBadge === 'E Standard' ? 'bg-green-900/30 text-green-400' : 'bg-yellow-900/30 text-yellow-400'}">${esc(tuningBadge)}</span>`;
                 if (song.has_lyrics)
                     html += `<span class="px-1.5 py-0.5 bg-purple-900/30 rounded text-purple-300">Lyrics</span>`;
                 if (song.user_difficulty != null)

static/js/settings.js

@@ -18,7 +18,7 @@
 // back-import would close a cycle. player-controls keeps reading it through the host seam, and
 // app.js — the root, which imports both — wires it. That is exactly what the seam is for.
 import { hwcInitSettingsUI } from './highway-colors.js';
-import { _getArrangementNamingMode } from './library.js';
+import { _getArrangementNamingMode, _setLibraryProfile } from './library.js';
 import {
     _applyMastery, _autoplayExitEnabled, _exitConfirmEnabled, _showUpNextEnabled,
 } from './player-controls.js';
@@ -111,6 +111,10 @@ export async function loadSettings() {
     if (dlcEl) dlcEl.value = data.dlc_dir || '';
     _defaultArrangement = data.default_arrangement || '';
     _syncDefaultArrangementSelect(_defaultArrangement);
+    // Feed the library its tuning PERSPECTIVE (lead / rhythm / bass) — the
+    // tuning facet, filter, sort and badges all answer for the profile the
+    // player actually plays.
+    _setLibraryProfile(data.active_instrument_profile);
     const pathwayEl = document.getElementById('setting-instrument-pathway');
     if (pathwayEl) pathwayEl.value = _normalizeInstrumentPathway(data.pathway);
     const demucsEl = document.getElementById('demucs-server-url');