Martin Loop and Jim Collins

MARTIN LOOP - Genres are not pure, they are a blend.
JIM COLLINS  - Hybridisation

MUMFORD AND SONS

Mumford and Sons performing 'I Will Wait' in 2012

Mumford and Sons performing 'The Wolf' in 2015

Mumford and Sons started off as a country/folk rock band when they released their first album (Sigh No More) in 2009 and their second album (Babel) in 2012. 3 years later, they released their 3rd studio album, Wilder Mind, which changed the genre of Mumford and Sons. They went from a folky rock band, to an alternative rock band. This completely changed how they were looked, and some were mad that they have changed their genre slightly, but some think it's the band just evolving. Looking at the 2 images above, you can see the difference in their image in the space of them years, they had traditional folk instruments on the top, but now you can see they have average rock band instruments on the bottom. In the top image, both Andrew Goodwin's and Martin Loop's theory apply to this. They were a a blend of folk and rock in most songs of the Babel album, and also shows they are a hybrid band.