The safest and most reliable way to obtain GarageBand 10.1.2 is through the Mac App Store using an Apple ID that has previously downloaded or purchased GarageBand in the past. Step-by-Step Instructions: Open the on your El Capitan Mac. Click on the Purchased tab at the top of the window. Sign in with your Apple ID (the account used previously).
Log out of the current user's Apple ID and . Search for GarageBand and click Get/Download . Garageband Mac Os X El Capitan 10.11.6 Download
– A fully featured DAW with a generous evaluation period and affordable licensing. Reaper runs efficiently on older hardware and operating systems. The safest and most reliable way to obtain GarageBand 10
Replacing an old mechanical hard drive with a Solid State Drive (SSD) drastically improves track loading times and prevents disk overload errors. Sign in with your Apple ID (the account used previously)
To run GarageBand on OS X 10.11.6, you need (or an earlier 10.1.x build), which was the final version officially supported on El Capitan.
If GarageBand is not in your history, sign in with your Apple ID on a newer Mac that is compatible with the current version. "Purchase" (download) GarageBand there to link it to your account. Once it is in your purchase history, return to your El Capitan Mac, go to the Purchased tab, and you should now be able to download the older compatible version. Compatible Versions for El Capitan
This is a common El Capitan bug. Pause the download, restart your Mac in Safe Mode (Hold Shift at boot), then resume the download. Safe Mode flushes the App Store cache.