Musical Mashup

Web app that produces a mashup of two songs by transferring the melody of Song A onto the timbre and rhythm of Song B.

Architecture

Component	Tech	Hosting
Frontend	React + Vite	Cloud Run
API	FastAPI	Cloud Run
Job queue	Cloud Tasks → Pub/Sub	—
Worker	FastAPI	GCE g2-standard-8 MIG (scales to zero)
Object storage	GCS bucket mashup-audio (input/, output/)	—
Job state	Firestore	—

Inference pipeline (worker)

1. Demucs v4 stem separation on Song A and Song B
2. Basic Pitch — extract MIDI from Song A's melody stem
3. Librosa — beat tracking on Song B
4. DDSP timbre transfer — synthesize Song A's MIDI using Song B's instrument timbre
5. Mix synthesized melody with Song B's drum stem
6. Upload result to GCS; update Firestore

Repo layout

.
├── frontend/   # React + Vite UI
├── api/        # FastAPI service: uploads, job submission, status
├── worker/     # FastAPI service: pulls from Pub/Sub, runs the pipeline
└── infra/      # Terraform for GCP resources

See each subdirectory's README.md for component-specific notes.