Comment by thclpr | Hacker News Reader

Comment by thclpr | Hacker News Reader

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I built StemDeck, a free and open source desktop application that separates songs into vocals, drums, bass, guitar, piano, and other stems. It started as a small project for my kid, who was learning bass and drums. Finding suitable backing tracks was surprisingly inconvenient. Most tools required an account, uploaded the audio to a remote server, imposed usage limits, or required a subscription. I wanted something simple that could process music locally.

StemDeck now includes:

- Local six-stem separation using Demucs - NVIDIA CUDA, Apple Silicon MPS, and CPU processing - Native releases for Windows, macOS, and Linux - Local file support for MP3, WAV, FLAC, M4A, MP4, OGG, and Opus - YouTube and SoundCloud imports - Direct search for YouTube songs, playlists, and SoundCloud tracks - Search-result previews before processing - Playlist imports and a persistent, reorderable job queue - A browser-based multitrack mixer with volume, mute, solo, and VU meters - Waveform navigation, zooming, and loop regions - Playback-speed and pitch-transposition controls - Automatic BPM, key, scale, LUFS, and peak analysis - A generated click track that follows the song - Custom mix, loop-region, individual-stem, ZIP, and video exports - A persistent local library with folders and search - A mobile-friendly interface accessible over the local network through a QR code - Docker and Unraid support - An in-app updater and nine interface languages

The backend uses Python, FastAPI, Demucs, FFmpeg, yt-dlp, librosa, and Web Audio. The desktop shell is built with Tauri. Processing happens on the user’s machine, and audio is never uploaded to a StemDeck service. There are no accounts, advertisements, subscriptions, credits, quotas, or telemetry. StemDeck is licensed under Apache 2.0, and I intend to keep it free and open source. It is still alpha software. Separation quality depends on the source material, CPU processing can be slow, and there are undoubtedly edge cases I have not encountered. Feedback, bug reports, architectural criticism, and contributions are all welcome.

> YouTube support is a convenience for content you have the right to process

Seems like a great way to have your project taken down

Agreed, this is a very silly thing to include in an otherwise perfectly legitimate project.

Why do you rely on ffmpeg and web audio? For this use case, Rust provides everything you need. It seems to me that this project is mostly vibe coded.

Rust could certainly handle much of the audio pipeline, but using Rust everywhere would not automatically make the application simpler or more reliable.

Other options may be available but for me FFmpeg provides mature, well-tested support for decoding, transcoding, resampling, mixing, and muxing across a wide range of formats. Web Audio handles synchronized multitrack playback, per-stem gain, mute and solo, metering, looping, speed control, and the browser-based mobile interface. Since the separation model already depends on Python and PyTorch, rewriting the surrounding audio stack in Rust would not remove the largest runtime dependency.

As for RUst itself its currently used for the Tauri desktop shell and process lifecycle. A native Rust audio engine may make sense later if it produces a measurable improvement in latency, memory use, or reliability, but replacing proven components purely for architectural consistency would add considerable complexity.

For the vibe coding part:

AI tools have assisted with development, and I am transparent about that. However, the architectural choices are deliberate, the code is reviewed, and the project has automated backend and browser testing. I would still welcome specific technical criticism or examples of places where the current design is causing real problems.

That's where my background kicks in, seasoned musician here with over 25+ year working on IT industry, so as i like to joke, im the maestro of the orchestra :)

On another words. i actually know how to cook , but to do it faster i need the assistances otherwise as a family man, I would never have the time to ship that and help my kid on a useful time.

I just want to say, kudos on your We Recommend section.

I was initially rolling my eyes at the "StemDeck... does not accept any money, sponsorship, or funding" line, here we go, another open source project that isn't thinking about practicalities... until I saw you were linking to others as pure recommendations. Just for the joy of what they do & how they've helped you and hoping they do the same for others.

The web used to have a lot more of that. It's a shame that doing so now often requires a disclaimer, and comes with the suspicion of being an influencer, or being done for SEO. And certainly many open source projects have done their part in corrupting the web too, accepting payment in return for SEO links on their pages. (Don't get me started on some of the things Mastodon accepted payment for...)

Thank you for bringing back that more hopeful, joyous part of the web and the music community.

That's actually the whole point for me. As i have no itention to monetize anything. Most people that are there are people that i Personaly know and that have a positive impact on my life or companies like empress/ Thoman that im a fanboy and their support has been amazing towards any product that i bought with them.

Look pretty. Can we load alternative stem separators like Spleeter, MDX-Net, and RoFormer implementations? I'd like to be able to AB them for different stems types.

Not yet. StemDeck currently ships with htdemucs_6s, and there is no general model-loading interface today. This is something I’m actively exploring. MDX-Net and RoFormer are especially interesting because different models can perform better on different instruments and mixes.

I agree that running the same track through multiple models and A/B comparing individual stems would be far more useful than presenting one model as universally “best.” The difficult parts are model licensing, package size, hardware requirements, and providing a consistent output format across models.

I also want to avoid making every user download several gigabytes of weights they may never use. The likely approach would be optional, on-demand model downloads with cached results and a model selector. So the short answer is no today, but alternative models and proper A/B comparison are absolutely on the roadmap. Contributions and model recommendations are very welcome thoyugh :)

Adding this to my homelab, thanks for the web browser option. How does your son use the backing tracks? Does he mute bass/drum, or play along with them?

Hello there, It depends actually, for what I hear from time to time when he is practicing, he sometimes plays with the original drums on default value or he loops into a section at lower speed and volume a bit down when he wants to learn an specific part. and when he feel confident he just mutes the drum completely :)

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