Provided you organize your media files into genre-based folders (e.g. 'Romantic Piano Comcerts'), you can have the 'genre' field auto-filled on import:
Go to "Options > Library & Folders > Configure Auto-Import", add your dedicated folder then click 'Edit' and under 'Apply these tags (optional) > Add > Custom' specify any field/value you wish, e.g. 'field=Genre' (to select from list), and 'value=Romantic Piano Concerts' (free entry).