Require key, instrument, tuning

app.js

@@ -504,6 +504,7 @@ function openAdd() {
   editingTuneId         = null;
   editingEntryId        = null;
   editingOriginalRefIds = [];
+  setTuneError('');
   $('modal-title').textContent = 'Add tune';
   tuneForm.reset();
   refsList.innerHTML = '';
@@ -659,11 +660,43 @@ function addRefRow(link = '', site = '', refId = null, siteId = null, initialMus
 
 // ── Save ──────────────────────────────────────────────────────
 $('btn-save-tune').addEventListener('click', saveTune);
-$('btn-cancel').addEventListener('click', () => tuneModal.close());
+$('btn-cancel').addEventListener('click', () => { setTuneError(''); tuneModal.close(); });
+
+function setTuneError(msg) {
+  const el = $('tune-error');
+  el.textContent = msg;
+  el.hidden = !msg;
+}
 
 async function saveTune() {
   const f = tuneForm.elements;
 
+  // Validate required fields
+  const keyVal    = f.key.value.trim();
+  const tuningVal = f.inst_tuning.value.trim();
+
+  if (!keyVal) {
+    setTuneError('Key is required.');
+    f.key.focus();
+    return;
+  }
+  if (!instrumentSelect.value) {
+    setTuneError('Instrument is required.');
+    instrumentSelect.focus();
+    return;
+  }
+  if (!tuningVal) {
+    setTuneError('Tuning is required.');
+    f.inst_tuning.focus();
+    return;
+  }
+  if (!resolveTuningId(tuningVal)) {
+    setTuneError(`Tuning "${tuningVal}" not found — use + to add it first.`);
+    f.inst_tuning.focus();
+    return;
+  }
+  setTuneError('');
+
   const tuneBody = {
     name:      f.name.value  || null,
     key:       f.key.value   || null,