Today Rinse FM, London's leading pirate radio station, announced it has been granted a legal broadcast licence after 16 years of illicit transmissions. It's almost impossible to overstate how potentially momentous this event is for the UK's most vibrant and promising music scenes, and what opportunities it presents for artists, personalities and record labels ranging from the deep and experimental to the most flagrantly commercial. From the rumbustuous, teen-friendly fun of Scratcha's breakfast show to the experimental electronic jazz and funk of Alex Nut at Saturday lunchtime to various hard and dark grime and dubstep shows - as often as not playing exclusive music fresh from the hard drives of its creators that may never even become commercially available - it is a brilliant representation of London's cultural vitality in the 21st century.

Quasi, Bye Bye Blackbird (Domino)

The "Bye Bye Blackbird" on offer here is not the jazz stalwart favoured by everyone from Peggy Lee to Miles Davis. It is, instead, a garage guitar-pop concoction from perennial underdog trio Quasi from Portland, Oregon, that prolific centre of American indie guitar raucousness. At the core of the band, ex-husband and wife Sam Coombes and Janet Weiss have always appeared happy, throughout eight albums, to veer into wilful lo-fi messiness whenever their natural aptitude for a tasty melodic song threatens to interfere. This time, though, they've blown it.

A little revolution is taking place at the top of the pop charts. UK artist Tinie Tempah's rap track “Pass Out” has had two weeks at number one, and at the time of writing looks very much like it may successfully fight off Lady Gaga & Beyonce's spectacularly-hyped “Telephone Thing” to make it a third week on top.

Amongst all the musical benefits for the victims of the Haiti earthquake, one club event which took place on Wednesday night in London stands out as a small, but powerful, beacon of hope. Not because it could rival Jay Z and U2 for levels of funds raised, but because it represented levels of commitment, self-motivation and unity among the capital's multi-ethnic youth subcultures that flies in the face of scare stories about gang violence, drugs, educational failure and all the rest of it. Raising well over £10,000 for Haitians, the entire event on Wednesday night at the club Den/Centro was pulled together in a mere three days by journalist and activist Chantelle Fiddy, promoters SOMEnight, and DJ Stanza of the Watford-based dubstep and grime label True Tiger, and went without hitch despite featuring on its diverse bill many grime rappers and DJs who find it difficult to perform in London due to police pressure on promoters. theartsdesk spoke to a dazed but happy Chantelle Fiddy yesterday to discuss the ramifications of the event.

The received opinion is that the music of the 2000s has been characterised by fragmentation, discontinuity, faddishness and a lack of coherent identity.

Rihanna, Russian Roulette (Mercury)

I strongly suggest anyone who believes the sound of US mainstream pop is somehow homogenised and safe take another look at the current charts. Standing over them like android colossi are Lady Gaga and Rihanna - who not only look exactly as pop stars were always going to look "in the future", but sound apocalyptically insane. This song is in the standard melodramatic modern power-ballad style of writer/producer Ne-Yo, but the combination of Rihanna's piercing voice and the lyrics that circle in the non-specific manner of nightmares around death, obsession, loyalty and points of no return - with (no shit, Sherlock) a heavy whiff of sado-masochism - make it an incredibly harrowing but addictive listen.  The flip side to "Umbrella"'s promise of protection, it's scary pop music for scary times.  "Russian Roulette" on Amazon. "Umbrella" on Amazon. (JM)

There are occasional days when the Royal Festival Hall really feels like the people's palace it was always meant to be – and yesterday, with its free concert of live improvisation mixed with dubstep and electronica in the RFH bar, was absolutely one of them. Rave kids, pensioners, parents with babes in arms and some particularly energetic school-age children all proved that given the right context music the border between “challenging” music and entertainment is more porous than some might like to believe.

Browsing through various past reviews of The xx, two adjectives which occur time and again are “fragile” and “tentative”. These are wrong – but understandable.