fix(tracker): recording creates empty track when no notes triggered

CHANGELOG.md

@@ -23,6 +23,8 @@ The format is based on [Keep a Changelog](https://keepachangelog.com/en/1.0.0/).
   ([#65][i65])
 
 ### Fixed
+- When recording notes from VSTI, no track was created for instruments that had
+  no notes triggered, resulting in misalignment of the tracks from instruments.
 - 32-bit su_load_gmdls clobbered ebx, even though __stdcall demands it to be not
   touched ([#130][i130])
 - Spaces are allowed in instrument names ([#120][i120])

tracker/recording.go

@@ -77,6 +77,12 @@ func (recording *Recording) Score(patch sointu.Patch, rowsPerBeat, rowsPerPatter
 			tracks[i][oldestIndex] = append(tracks[i][oldestIndex], n)
 		}
 	}
+	// if there was tracks that had no notes, create empty tracks for them
+	for i := range channelNotes {
+		if l := len(tracks[i]); l == 0 && l < patch[i].NumVoices {
+			tracks[i] = append(tracks[i], []recordingNote{})
+		}
+	}
 	songLengthPatterns := (frameToRow(recording.BPM, rowsPerBeat, recording.TotalFrames) + rowsPerPattern - 1) / rowsPerPattern
 	songLengthRows := songLengthPatterns * rowsPerPattern
 	songTracks := make([]sointu.Track, 0)