List audio clips you previously generated through the API, most recent first. This is a free read-only history lookup (no credits, no generation); it does not create anything. Pass an optional request_id query parameter to return only the results tagged with that id when you originally called createSoundEffect, createAmbiance, createMusic, createAudioTransform, createVoice, createSpeech, or createSpeechPreset. Requires an API key (user scope).