This reminds me of Whisper, one of my favorite exotic alien concepts. The alien civilization in question has selected a planet with as stable environment as possible, and planted it full of genetically engineered grass. The sound of wind blowing through the grass creates an acoustic computer which hosts a virtual space its creators have uploaded themselves into.

https://www.orionsarm.com/eg-article/470007b39d192

I have never heard anything like that (using sound) before. Amazing!

A SF short story about a biologically encoded message from ancient aliens (written by one of the Autodesk founders): We'll Return, After This Message by John Walker

https://www.fourmilab.ch/documents/sftriple/gpic.

It's fascinating that in 1983 it was thought that a 768-bit RSA number would take 40 million years to factor. (It actually took 26 - RSA-768 was factored in 2009.)

The link seems broken? Should be: https://www.fourmilab.ch/documents/sftriple/gpic.html

Or directly encode the message in DNA itself. I suppose the difficulty would be devising an encoding with enough redundancy or other features to preserve the information content over many generations of evolutionary pressures.