btw Catalina 10:15:2 that will work with my Steinberg RT2 interface and GB ,yes??

(Quote) btw Catalina 10:15:2 that will work with my Steinberg RT2 interface and GB ,yes?? (Unquote) New topic—see the new thread..

I couldn't figure out how to cancel this download either. Fortunately, I found the Garageband preferences plist file, which contained a list of active downloads. To make Garageband 10.3.4 stop downloading on Catalina (10.15.3), I did the following: 1. Quit Garageband 10.x 2. Open Terminal (find it in the Applications => Utilities folder, or you can use Spotlight and search for "Terminal" by name) 3. Run this command in Terminal to remove the download list from the preferences file and make Garageband forget that it was downloading anything (type the following and press Enter): defaults delete ~/Library/Containers/com.apple.garageband10/Data/Library/Preferences/com.apple.garageband10.plist MAPrefs_ActiveDownloads_2 4. Relaunch Garageband. Whew! Download stopped! (To restart the download, select Garageband >> Sound Library >> Download All Available Sounds) Note: I could not find where it downloaded the files to recover any space. Garageband had already downloaded maybe 1GB of the sounds when I stopped it. The "MAPrefs_ActiveDownloads_2" list consisted of many packages; it might have even been installing them as each package downloaded. I suspect some of that first 1GB went into "/Library/Audio/Apple Loops/Apple Loops for GarageBand", as its modified date was set to today. I hope this helps others recover from Apple's failure to put a (x) cancel button in Garageband's very slippery download window! (Even though I realize the OP's problem was resolved by completing the download over faster internet!) -Bill ps. "defaults" has been a useful command to read, write, and delete properties in Mac OS X property list (plist) files. To learn more, try running "defaults --help" or "man defaults" in Terminal.

Hi Bill - Just FYI, the downloaded GB Library is stashed in "Library/Application Support/GarageBand"—it's around 14GB or so, so it's actually not too massive (as you saw, the Loops are stored separately, another 300MB). (At least I assume that's what you get from GB alone.. I had Logic installed before I installed GB—Logic uses the GB samples as well, in addition to its own (~70GB) of Library sounds (& loops), which does make a significant dent in a smaller startup disk, like, say, a 256GB SSD that comes with some of the smaller Macs). In Logic, Apple is nice enough to include Sound Library Manager, which lets you install those individual packages (over & above the required 2GB of Essential Sounds) manually, selecting only the ones you want—I guess they felt that 14GB wasn't enough space to worry about, but 70GB was. Logic also now provides an option to lets you move its Library to another drive, added in response to years of user complaints about the 70GB install eating up too much space in the required install location on smaller startup drives.

If there is an active download there will be a blue bar underneath the time signature area (top center of the main window). Clicking it will bring up the list of downloads and you can cancel it there.