Add starter structure for demucs/tts demos and .gitignore

Co-Authored-By: Claude Sonnet 5 <[email protected]>
Claude-Session: https://claude.ai/code/session_01SN15Vxn4svKuhYxFsVtMJf

README.md

@@ -1,3 +1,15 @@
 # audio-demo
 
-Audio processing demos: WhisperX, Demucs, and TTS technology proofs-of-concept.
+Audio processing demos: WhisperX, Demucs, and TTS technology proofs-of-concept.
+
+## Structure
+
+- `whisperx/` — speech-to-text with word-level alignment and diarization
+- `demucs/` — source separation (vocals/instrumentals stem splitting)
+- `tts/` — text-to-speech service demos
+
+Each subdirectory has its own README with setup and run instructions.
+
+## Requirements
+
+Some demos are GPU-accelerated and are best run on a CUDA-capable machine (e.g. an RTX 3090).