I want to create music-controlled visuals to provide that required component of a YouTube video, preferably with MacOS software.

There are "educational" apps that show notes dropping onto a piano keyboard, but I'm more interested in a basic, fun light show. I would just play my music in Apple's Music app and record its Visualizer, but I am unconvinced after all these years that there's any connection at all between what that thing is playing and those animations! Anyway.

I'm not looking for anything fancy, certainly not looking for a development environment in which to produce animations, just something to provide visuals that sync with the music and are better than a black window.

OK, there is this, for MacOS, MIDI only:

MIDITrail – https://apps.apple.com/us/app/miditrail/id421739418

https://youtu.be/CuLYhaI6oeY

I like the circular keyboard, and the "airplane flying over islands" effect is pretty cool.

https://rotorvideos.com/product

There's a visualized built into iTunes/Apple Music that's pretty cool — and free. If you want to add it to your video, there are a number of screen recorder apps that can do this including QuickTime but that's a bit of a pain to set up.

Yeah, but there's rarely any obvious connection between the music and the visuals! There will be big dramatic action with giant glowing globules colliding and exploding, but it has nothing to do with the sound; the only thing responding to sound is a faint little wiggly green line off to one side.

VLC has visualizers, too, it turns out, that are a lot more obviously reactive.

Checked it out, screen-recorded a preview. All I added was chickens, everything else is Rotor's clips. If you skip to the last 30 seconds or so, it gets pretty intense:

https://www.youtube.com/watch?v=wczcvliRUjg

Way cool, though not a lot of obvious interaction with the music. And pricey to download! But I know I'll be back in there.

Thanks for the tip!

Mark, I've not used it myself. An acquaintance from another forum started using it and gave details so I copied & pasted. Not much relationship with anything in the music really - though it does add to the intensity as you mentioned. It may be one of those things that work really well one song and is useless on the other.