I need a browser-based karaoke application that runs smoothly on both desktop and mobile browsers. The core flow is simple: users land on the site, upload their own song or backing track, hit “Sing,” perform in real time, and receive a mixed recording (their vocal plus the track) to download or share. Key requirements • Web platform only – no native mobile or desktop builds. • User-supplied content – there is no internal song library; every session starts with an upload. • Integrated recording – record the backing track and microphone simultaneously, then output a single audio file. Low latency and volume balancing are essential. Implementation details I’m happy to leave tech stack choices open, but the front end must be responsive and modern (React, Vue, or plain JavaScript are all fine). On the back end, Node.js, Python, or another lightweight solution is acceptable as long as you document setup and deployment. Using the Web Audio API, FFmpeg, MediaRecorder, or a similar tool to handle the recording/mixing is expected. Deliverables 1. Fully functional web app deployed to a test URL. 2. Clean, commented source code (Git repo or ZIP). 3. Step-by-step deployment guide so I can move it to my own hosting. Acceptance criteria • A user can upload an audio file up to 10 MB, press record, sing along, and download the final mix within the same browser session. • Recording quality is at least 128 kbps MP3 or AAC, with clear vocal/instrument balance. • Interface loads and operates without errors on Chrome, Firefox, Safari, and mobile equivalents. Future roadmap items like lyrics display or live streaming aren’t in scope yet, but building with extensibility in mind will be a bonus. Let me know which tech stack you prefer and any similar projects you’ve shipped.