These are the packages that would be merged, in order:

Calculating dependencies ... done!
Dependency resolution took 0.84 s (backtrack: 0/20).


!!! All ebuilds that could satisfy "=app-accessibility/mbrola-voices-0_pre20200331" have been masked.
!!! One of the following masked packages is required to complete your request:
- app-accessibility/mbrola-voices-0_pre20200331::gentoo (masked by: MBROLA-VOICES license(s))
A copy of the 'MBROLA-VOICES' license is located at '/Volumes/Disk 1/Repository/portage-git/licenses/MBROLA-VOICES'.


For more information, see the MASKED PACKAGES section in the emerge
man page or refer to the Gentoo Handbook.