Since breaking through with her 1992 debut album Dry, PJ Harvey has constantly been on the move, changing and evolving, both musically and sartorially. Last night at the Troxy in East London was no exception. As she walked onstage dressed in a long black frock with a riot of matching feathers exploding from her head, she resembled Lady Gaga's bonkers West Country Edwardian ancestor.

There are some glorious sounds to be heard in the world of music: a big band in full swing; a symphony orchestra in full flight; a gospel choir; the Hammond B3 organ. But to my mind there’s nothing quite like the sound of a line of electric guitars – not chugging along like the Quo or Lynyrd Skynyrd, but meshing, interweaving, thrumming, humming, threshing, shredding, screaming; like Mogwai.

Rap audiences are not renowned for being easy to please – but it's a daring performer indeed who is willing to stand up and drop lyrics in front of some couple of hundred babies and toddlers. Yes, as television's Rastamouse has brought reggae culture to Ceebeebies viewers, so this week DJ, promoter, teacher and poet Charlie Dark has been breaking down the elements of hip-hop for those who are more pre-school than old-school.

Rock-folkies can sure be snobs. Even though New Hampshire-born Ray LaMontagne is still relatively unknown over here, there are still purists who view his records with suspicion. They feel the voice is just too huge, the sound too commercial. The irony is that no-one courts attention less than LaMontagne. Last night he delivered the entire concert from a static spot just to the left of the band. And apparently he’s as withdrawn offstage as he is on. But the RFH saw him focussed. Focussed on finding the right way to channel that part-bluebird, part-bear he has for a voice.

This month's Singles & Downloads leads off with a new one from an absolute kingpin of US pop and hip hop. However, the focus is equally on the backwaters and curious places where other lively varieties of music dwell. From dancehall raucousness to erudite indie, from ranty punk to funk reinterpretations of American minimalist composition, all pop life is here and keenly assessed by Thomas H Green and Joe Muggs.

It’s the convention to review concerts on the first night of a tour rather than the last, but in this case it transpired it was rather wise to make an exception. These two groups may make very different kinds of music, but in their questing desire to escape classification last night they seemed to share a certain esprit de corps which added to the sense of occasion.

When it comes to the Seven Ages of popular music we are now well into the post-retro era. In 2011 every artist is a magpie and every song sails out beneath a pirate flag, greedily plundering where it pleases. When everything that has gone before is up for grabs, it’s now simply a question of how you want your yesterdays delivered: rare, medium or well done?

Avant-garde art, by its very nature, always treads a fine line between the sublime and the ridiculous, and between entertainment and alienation. Thankfully this is something understood very well by the joint curators of Friday night's show at the Vortex Jazz Club: Baron Mordant of the Mordant Music record label and Jonny Mugwump of the Exotic Pylon website and radio show. As the names perhaps suggest, these are people versed in the potential deep silliness of what they do, even as they take it very seriously indeed – and their event certainly ranged far and wide between the weird, the wonderful and the out-and-out wrong.

As a world music critic one gets used to the stream of superlatives that generally arrive in the wake of whatever big new act is being plugged. World music promoters have a particularly hard job because they don’t just want to preach to the converted; they also want to try to get some new listeners to widen their musical horizons a little. So even before I’d heard a note of the Creole Choir of Cuba I knew that they’d gone down a storm at the Edinburgh Festival, that Jools Holland’s producer wanted them for Later..., and that they were booked to do various BBC radio sessions.

Every February the Sadler’s Wells flamenco festival summons the illusion of Spanish sun onto our chilled, grateful backs - this year singers are getting almost as much prominence as dancers. But what sun, I ask, at Estrella Morente’s dark, often remote evening, opening the fortnight last night? (And why, still, after years of urgent requests, no subtitles for these pungently melodramatic lyrics?)