Using Join Together
Notes & FAQ

I've successfully tested joining files up to twenty-two hours in length (the file size of which is ridiculously large). Things may get a little bumpy during the "Finishing Export" stage on very long joins. Your mileage may vary. I wouldn't attempt to create very long ALAC files as these can be very large.

You should never upcode—that is, don't think you can get higher-quality audio by setting the Output Settings' Bit Rate higher than the source tracks' bit rates. Try to stay near the same bit rate or lower.

Passes. With flying colors. Of course, quality source files are essential.

Currently, only MP3, AAC, ALAC (Apple Lossless), WAV and AIFF (and AIFC) formatted audio files can be joined. Future updates may accomodate additional formats.

Join Together logs status, progress and error messages to Console.app. It gives a pretty good picture of what goes on so checking Console.app even while the app is running can be helpful.

In case you don't know, Console.app is located in Applications/Utilities/. Launch Console.app. If nothing Join Together-related appears listed, try typing "Join Together" in the search field of Console's toolbar and then press the "Return" key to display only the messages that mention it.

Yes. AIFF files from a CD are very big and data on physical CD media takes longer to access than data on a hard drive.

You could try, but I can't enthusiastically recommend it because the additional encoding may result in audio degradation. On the other hand, this may not be as much of a consideration for voice recordings as it might be for music.

Under macOS 10.15 Catalina and later, final joined files will be added to the either the Music app or the Books app depending on the Media Kind selected for the joined file. Using iTunes, final joined files with a ".m4a" extension will be added to iTunes' "Music" Library. Files with a ".m4b" extension will be added to the "Audiobooks" Library. There is no getting around this.