It worth bearing strongly in mind that the human brain tries very hard to make sense of what is sees and hears.
That's why we see faces in fairly random shapes and blotches in toast, fruit, tree trunks and what have you, and why we start to hear, or think we hear voices in almost anything that's at a vocal-region pitch and even faintly in white noise.

It always puzzled me why anyone would play music backwards looking for hidden messages.

If one really wants to make a reverse message, a vocoder-type device would be an easy way to do it. Reverse the sound, code it, play it forwards.

Jazz relative beginner, starting at a much older age than was helpful.
AVL:MXE Linux; Windows 11
BIAB2025 Audiophile, a bunch of other software.
Kawai MP6, Ui24R, Focusrite Saffire Pro40 and Scarletts
.