If you're running a music blog, you might want the route to be /genre/ rather than /tag/, and perhaps you'd rather the route be /by/ rather than /author

Edit routeKeywords at core/server/config/index.js

routeKeywords: {  
             tag: 'genre',
             author: 'by',
             page: 'page'
         },

Then restart ghost application.
If you use Systemd or Init.d script you can easy restart Ghost.

service ghost restart