Google → Question about Android File Transfer

I'm planning on buying the S21 Ultra and it does not have a microSD card slot. I downloaded Android File Transfer but I never used it before.

Where do I place my music files in the phone? (I'm going to be using both Poweramp and the Sonos app to play music) I haven't transferred files like this in many years and am a little rusty. Thanks.

Why not just plug the phone into your computer and transfer them that way?

Yes, that is what I'm going to do. Android File Transfer is the software for my Mac to do it.

What is your current phone? When I got a Google Pixel 4a to replace my Moto G5+, the Pixel came with a USB-C to USB-A adapter. That let me plug the Moto cable into the Pixel. During the Pixel setup it asked if I wanted to transfer data, and it either triggered or copied a program to the Moto to do that. It copied everything over, including a Music folder that was on an SD card in the Moto.

My current phone is the S10+. I want to be able to constantly transfer music files from my Mac to my new phone. The S21 Ultra comes with a USB-C to USB-C cable. So I attach that to my Mac and from what I've read install Android File Transfer on my Mac to transfer the files. Is that incorrect?

Edit: Sorry, I probably didn't describe my issue that well in my OP.

I thought you were talking about transferring data from your old phone to your new one.

There should be no difference between syncing between a computer and any phone. I think the OS is smart enough to detect music files and will default to there. Most of mine ended up in a folder named "Music".

Not sure what you use to play it. Google disabled Play Music and replaced it with YouTube Music. It technically supports playing on-device music, but it's useless if you have more than a few songs. I have around 6400 files, and it doesn't work at all. I ended up using MediaMonkey. I also have the Windows version and use it to keep the two in sync. I don't know if there is a Mac version. The paid versions allow WiFi sync, which is a bit faster and works better at keeping some of the data properly synchronized.

Thanks...I use Poweramp which can handle all of my songs. I have about 5000 files. The reason I thought that I had to use the app Android File Transfer on my Mac is because I read it in a legit Google article to use it. If Big Sur itself can detect the S21 Ultra's OS and file system that will be great.

When I plug my phone into the computer I get a popup on the phone asking if I want to charge the phone or transfer data. When I select transfer data, the phone storage shows up in the file manager. MacOS is probably the same.
How old was the source that said to install the app?

I concur, i have been able to access files on my android without an app since 2013, never tried before that cus never owned an android before that year