Logic Pro's ".bundle" sound library file is twice the size of what Logic reports the sound library to be in-app.

This is how Logic's library gets created and built after installing the app.

Upon installation, the user is asked to install three particular starter packs. These are the first to be installed and bring the library.bundle to a size of just over 3 GB.

When you launch Logic and now go to Logic Pro > Manage Packs to install "All Available Packs" you get the Sound Packs, Artist & Producer Packs, Instrument Packs and Session Player Instruments & Loops. This grows the

library bundle size to about 45 GB.

But that "All Available Packs" total size is misleading as it excludes 18 additional packs at the bottom of the list. Manually select and add these "Essential and Compatibility Packs" that include several Jam Packs, Alchemy packs, Garage Band Legacy, Logic 10 and Logic Pro Legacy Packs and the library bundle now sits at over 86 GB.

So, nothing duplicated per se, just some things not accounted for.

Logic Pro's Library.bundle contains more than just the sounds found in the Sound Packs.

So while Logic Pro reports All Installed Packs to be 44.09 GB, the total file size as reported by Finder is much larger.

My library.bundle is ~87 GB total size according to Finder.

About the Logic Pro and MainStage sound library on Mac - Apple Support

❝Starting in Logic Pro 12 and MainStage 4, all sound library files included with Logic Pro and MainStage such as software instrument patches, Apple Loops, and samples are stored in a single file called "Logic Pro Library.bundle." The new file streamlines sound library workflows like using your sound library on other computers and relocating your sound library to an external storage device.❞ - Apple Support

g_evan_c wrote: So.. what else exactly is in there? Because as far as I am aware, the sound packs include all those things; instruments and their samples, loops, patches... so either I'm wrong or there's something extra that I'm missing.

You are not wrong. The packs do include all those things and you aren't missing anything.

Logic's developers just haven't correctly integrated all the available packs into the library manager and installation process. Apparently to them "all" equates only to "most" and we users are left to clean things up after.