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Claude Fable Reverse-Engineered PianoDisc's 2004.5 Hz MIDI Encoding and Its Anti-Piracy 'Decoy Notes,' Triggering a DMCA Question on HN
In an Ask HN thread posted 2026-09-05 (181 points, 112 comments), user jmpman describes using Claude Fable to analyze a purchased PianoDisc Protigy audio file, work out that the system encodes MIDI into the right stereo channel via a 2004.5 Hz square wave, and generate working Python encoders and decoders. Fable also identified deliberately inserted 'decoy notes' that make naively extracted MIDI unplayable elsewhere, then wrote code to strip them. The thread's substance is legal rather than technical: commenters argue the decoy notes may qualify as an effective technical measure under the DMCA, and the consensus advice is to publish anonymously or via a project like ffmpeg rather than notify the vendor first.
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