You can install Microsoft's natural voices, which will be able to work offline. After installation, the voices will be available in any application that uses SAPI 5 (for example, in the Balabolka application).

Spanish (Spain) voices:

- Microsoft Abril Native (female)
- Microsoft Alvaro Native (male)
- Microsoft Arnau Native (male)
- Microsoft Elvira Native (female)

Official website of the Balabolka application:
https://www.cross-plus-a.com/balabolka.htm
