Oh man, lots to think about here. So a cassette deck should be able to record ultrasonic frequency, the max frequency is like 20kHz. But playback might be inconsistent so I will try.

Second, I have thought about the diy cassette deck already 😀 It is a bit complicated to do cemetery from scratch these days unfortunately. Although, I would love to build a cassette deck product... but anyway, so if we assume there is a cassette deck with line or headphone out, this gets easier.

So this next issue, which comes out in 1.5 week you will like the experiment I do. I send a qr code over audio :) and it will show up on your phone like a fax. It is audible though and takes 2 minutes.

I did however add the nostr qr codes for the contributors on the cassette cover for me, nostr:nprofile1qqsf37qcuu353dsyqaawqjdg8rr7vm7srchr76x9uqh3zfv2yuz07pqpg3mhxw309ahhsarjv3jhvctkxc685d35093rw7pkwf4xwdrww3a8z6ngv4jx6dtzx4ax5ut4d36kw6mwdpa8ydpkdeunyutzv9jzummwd9hkutcpz4mhxue69uhkummnw3ezummcw3ezuer9wchszythwden5te0dehhxarj9emkjmn99uyn6674 and nostr:nprofile1qqs0cu4wf0x3g99dg0qz795j5taln5caux0929tkazem59pd9wqkm0sprpmhxue69uhhyetvv9ujucm4wfex2mn59en8j6f0qy88wumn8ghj7mn0wvhxcmmv9uq3xamnwvaz7tm0venxx6rpd9hzuur4vghs7jwvrz so people can follow / zap. It is however just static not linked to the content (but the track list credits the artists).

If we add a mixer with a high pass filter, the data bits could perhaps be filtered to go to this lcd and the rest of the audio goes to the listener. I think this is basically Dolby noise reduction but in the other side of the spectrum.

Love the idea though, thanks for your thoughts. I've been noodling something like this.

Lastly, I submitted a talk for HCPP in prague in October so if accepted this would be a Cool thing to demo there.