Wired into the time of Set sound FX parameters, a change then spans exactly one run of the clip, so a fade or a filter sweep ends with its last sample. - Play sound has a second output, length, in seconds. It is 0 where nothing was played or the sound has not loaded yet. - The AudioSink gives the length of a file, the SoundLibrary takes it from the decoded buffer. A pitch the voice starts on keeps it (#312). - A pitch changed while the voice plays still changes its length, so a pitch sweep over length does not end with the sound. A pitch that keeps the length in real time is #317. Tests: - soundfx, sounds, keep-on-scene-load, node-catalog, sound-library: 462 tests green. - Counter-check: with length always 0, the catalog case and the new soundfx case fail. Co-Authored-By: Claude Opus 5.5 <noreply@anthropic.com>