Original teaching composition: 30 seconds, 24000 Hz mono. Three synthesized stems and stock Windows synthetic narration. Import all at time zero; no tempo stretching. Music is an original demonstration, not a model output or commercial song. Practice: trim to 15 seconds, fade the ending, export a stereo mix and three separate music stems. No named editor was benchmarked. Narration starts at 4 seconds. Microsoft David Desktop synthetic voice; not a human interview. Keep source files unchanged.