Ask HN: Fable hacked my piano, can I release the results?
149 points - last Saturday at 2:54 PM
I have a self playing piano, using a system called PianoDisc Protigy. They have an online store which sells music for their system, from various modern artists along with classics such as Bach and Beethoven. Last night I saw they had released some music from Eric Satre, a 19th century French composer, which I bought. Curious if I could have just used AI to create these files, I began experimenting with Astra and Fable. Feeding the output of one into the other to critique. After an hour of LLM discussion of Rubato and fermata, solenoid response times and proper sustain pedal technique, they settled on their ultimate version of Gymnopedie No 1.
I then asked Fable to compare it to the open source version I'd downloaded from Mutopia, which it promptly ripped apart. No sustain, zero rubato, upside down balance.
Ok, what about the version I'd just bought?
The PianoDisc versions are mp3s encoded with the right channel carrying MIDI to be played on the piano, and the left channel containing any accompanying music to be played through attached speakers (who doesn't want the harmonica on Piano Man?)
I gave the mp3 to Fable, which promptly decoded the format, identifying the right channel carrying MIDI using a 2004.5 Hz square wave.
It then went on to analyze the nuance of pedal lift and melody relative to the chords.
Fable then asked if I wanted it to build an encoder to write my own MIDI files into the right channel of mp3s.
Sounds great, and I instructed it to write the encoder.
What it came back with was a python encoder PLUS a decoder.
In the verbose explanation, it mentioned decoy notes.
Curious, I asked it to explain the decoy notes.
Apparently PianoDisc adds obfuscation into their format which is handled properly by their decoder, but would leave naively extracted MIDI unplayable on other systems.
Fable created an encoder which adds those decoy notes, and a decoder which removes them.
Am I allowed to publish the decoder? The encoder?
Comments
If you live in Europe, this restriction may be considered "gatekeeping" and exempted by the Digital Markets Act.
Don't bring attention to yourself by asking for permission. Publish your codec, and if the company cares about this they will send a cease and desist.
If you want the world to benefit from your code but you don't want to be responsible for it, try to adapt the codec to ffmpeg. The ffmpeg project is used to dealing with these matters, and will keep your codec working for eternity.
Likewise, if you're able to upload your own custom MIDI (or other) files for your piano to play, then all you'd be doing is sharing a utility that creates mixed audio/MIDI MP3s, which may or may not be used to create files which can then be legitimately uploaded to a piano.
If it matters, ask your lawyer.
If it doesn't matter, it doesn't matter.
Or to put it another way, trademarks (you've mentioned two) and copyrights (it's a crapshoot) are complex. And in some jurisdictions (notably the US) anybody can sue anyone for anything.
Your risk aversion is yours, not someone else's. Your financial and legal wherewithal is likewise yours.
> The dataset contains about 200 hours of paired audio and MIDI recordings from ten years of International Piano-e-Competition. The MIDI data includes key strike velocities and sustain/sostenuto/una corda pedal positions. Audio and MIDI files are aligned with ā¼3 ms accuracy and sliced to individual musical pieces, which are annotated with composer, title, and year of performance. Uncompressed audio is of CD quality or higher (44.1ā48 kHz 16-bit PCM stereo).
What a cursed format!
I don't understand what the designers were thinking of... 2000 Hz square wave on right channel? Seriously? Nobody would hear something suspicious and nobody would literally see it on spectrum analyzer. Maybe it's holdover from analog days and it was on casette tape before.
Also somebody reverse engineered it before - https://www.kinura.net/mid2pianocd/
So Fable probably just igested it from documentation of this software or some very obscure forum thread somewhere.
If your goal is to not pay them money - which you strategically unwisely hinted at with this question - then that's not covered by that exemption, I think.
So from my understanding, adding new music and releasing the tooling for that should be fine, but IANAL.
Frankly, what is or isn't legal doesn't matter as much as your story, as you will be judged by that. It also helps if the story is actually genuine, but that is a somewhat optional requirement all things considered. At least the industry treats it as such.
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FWIW, as these capabilities trickle down to everyone through LLMs, it is worth asking yourself whether it is worth the trouble of releasing it in the first place.
If anyone can replicate this within a reasonably short timespan, then maybe not.
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With this stuff in particular, it's also worth considering the business model of the entity.
Does your work pose a relevant risk for their bottom line? If yes, then bad. If no, then shrug.
Is music sold their main revenue channel, or are they just also doing that because recurring revenue is nice to have?
How user-friendly would you want your work to end up as? Would it target the demographic that would otherwise just buy the music?
Truth is that this is all just an elaborate dance.
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To close the "polish trains" gap in what I just wrote in the last section:
"Is their business model ethical? And is it considered that by the majority, common sense, and politicians?"
> Gymnopedie No 1
Eric (or as he preferred, Erik) SATIE.
Now its likely soiled and I have to throw it away. Doh! I asked it about legality and it went "its almost green" but when googling, reverse-enginnering like that seems very illegal.
The weird thing is in this case, it could have pretty easily gotten the needed info from using the code as a black box, and that is apparently legal!
Also, when you bought from PianoDisc, did you agree to abide by a certain jurisdiction's laws in your use of PianoDisc? And did you explicitly agree to not share any sort of decoder/encoder in any ToS?
This decoy notes scheme seems pretty unethical.
If you sell your decoder or encoder the company will, eventually, kick your butt. Getting money involved raises the stakes.
If you distribute a file that is sold by the company, even if it was transformed by a decoder, the company will, eventually, kick your butt. (A recording or sample of how it sounds post-transformation for demonstration purposes would be reasonable.)
If your software requires files that must be paid for in order to function, then itās critical that you do not bundle those files with your decoder or encoder. That would be piracy.
How your software was made matters. Did you have access to non-public information about anything involved? It seems like the answer is no, so you might be fine. It sounds like you legally obtained a copy of the file, hardware that runs it, and figured out how they work.
What terms of service did you agree to? While not everything listed may hold up in court (which gets determined BY a court IN a court so donāt think thatās an easy win), the company is surely within their rights to ban you from their online service.
If you want some relevant legal advice, check out the GameCube Dolphin emulator and how the team stays legal. I love learning about how stuff works, so Iāve followed lots of console jailbreaking and reverse engineering news for years. There is a way to do this stuff legally. HN is focused more on finance than hacking. So talk to some hackers (who arenāt trying to break the law).
I saw you ask about contacting the company. If this was a blog, Iād love a followup about what they say and do, but alas Iāll probably never see it. (I guess the worst outcome is that they spend more money on making their proprietary stuff more locked down?) Regardless of what they say, their word is not the law. Know the law, know your rights, and know when itās safe to stick your neck out and when itās not. I am obviously not a lawyer.
Oh, and which US state you are in and what they are based in will be relevant.
On a serious note: reverse engineering is legal in australia, even for DMCA violations.