The agency has been appointed non-competitively, and will use media relations to raise Last.fm's profile and show that it is not competing with Spotify.
A Propeller spokesman said: 'There's a view out there that they are competing with Spotify, but Last.fm is more of a social media channel while Spotify is focused on delivery of music.'
The agency will also be helping to promote Last.fm's recently-launched Œpersonalised visual music player¹ and further technology developments, while updating business on Last.fm's advertising opportunities.
The account is being led by MD Martin Loat, who reports to Last.fm senior vice president and head of international sales Miles Lewis.
Founded in 2002, Last.fm is a CBS Corporation-owned free global music platform with 30 million users worldwide.