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Continue to ChatRockin’ Patent – Josef Hofmann’s “Recorder for Musical Dynamics” https://www.russellip.com/rockin-patent-josef-hofmanns-recorder-for-musical-dynamics/
Rockin’ Patent – Josef Hofmann’s “Recorder for Musical Dynamics” https://www.russellip.com/rockin-patent-josef-hofmanns-recorder-for-musical-dynamics/