Stamp each line to the moment it lands, fine-tune by ear, then export the timing your player reads. One song, once — and the words are locked to the music forever.
Local files are most reliable. Playback works either way — nothing is uploaded anywhere; this runs entirely in your browser.
LRC is the universal synced-lyric format — keep it as your master. JSON is the shape the player loads. Drop the file into assets/lyrics/ when we wire the panel in.