While GarageBand 10 is the current standard, many veteran users prefer version 6.0.5 for several key reasons:

Before downloading, you must verify that your Mac's operating system can actually run a 32-bit application. I have Garage Band 6.0.5 - Apple Support Community

A unique feature that allowed users to quickly assemble a virtual band to jam along with.

If you have the original iLife '11 physical DVD, you can install it from there and then use the Apple Support Downloads page (if still hosted) to apply the 6.0.5 update.

Many of the quirky, predefined vocal and sound effects were removed in the transition to version 10. How to Download GarageBand 6.0.5 Legally

If you are looking to download and install this specific version, here is the essential guide to finding it, checking compatibility, and understanding why it’s still a top choice for many musicians. Why Musicians Still Download GarageBand 6.0.5