How to exclude specific folder 'Music Folder' from migration transfer on MacBook Pro

Unfortunately Apple's Setup Assistant/Migration Assistant is an all or nothing transfer and only allows you to select migrating particular user accounts, but not particular items within those user accounts.

After creating a new macOS user account in the fresh OS, you can manually transfer your items to the new Mac using Target Disk Mode or through File Sharing, or by launching the Time Machine backup software and select which files to restore. You can also transfer the items to an external USB3 drive which can sometimes be easier than using Target Disk Mode or File Sharing.

I hope you backup your computers. With the newer Macs there are a lot more new ways to permanently lose access to the data on the internal SSD due to all the hardware, software, and security changes.

BebopLondon wrote:

My intention is to erase the 'music folder' on the 2011 M/B H/D which will reduce the data by 50GB and then use the Migration Assistant to migrate to the 2020 M/B. I'm assuming the migration will not include the system files on the 2011 M/B. If that's true, then I should have more than enough space. Please le me know if you agree.

System files are not transferred. You can select various categories to migrate such as macOS user accounts, Applications, Settings, and I believe there may be some other items that can be selected or deselected.

If you want to use the Music folder on an external drive, here is an Apple article with instructions:

Change where your music files are stored on Mac - Apple Support

There are similar instructions for Photos & Videos Libraries as well.

I now have a question about Time Machine. I have been successfully backing up the 2011 M/B on a 'My Book 3T' drive. After the migration, the 2011 M/B will be dedicated to my music studio work. The external drive named Drive 2024 1T, containing my 'Music Folder' will stay connected to the 2011 M/C (which has 2 USB ports). When I back-up, I would like to connect 'My Book 3T' backup drive to the second USB port and have Time Machine back-up both the 2011 M/C HD and the attached external Drive 2024.

In Time Machine preferences I got as far as having Time Machine recognise both: M/B HD and Drive 2024 but when I selected back-up for Drive 2024 the message said backup would take 5-6 hours! I got frightened because I worried that Time Machine was going to back-up both M/B HD and external Drive 2024 onto Drive 2024! The connected MyBook Backup drive is 3T so can easily take both. I disconnected both drives to stop any further progress but Time Machine is now displaying the message 'waiting to complete the first back-up' next to Drive 2024.

It is possible to have Time Machine backup an external drive. I don't use TM, but I did find this article with instructions:

https://www.macworld.com/article/229391/how-to-make-sure-time-machine-backs-up-external-drives.html