This is where the delirium kicks in. Tired but happy, the attendees started the third day of Sónar festival slightly boggled by how to pick and choose from the strange delights on offer. Saturday was when the true musical variety of the festival was displayed: straight-up hip hop to eye-popping South African tribal dance displays, balmy ambient revivalism to apocalyptic techno, heartbroken electronica to deranged prog rock: it was all on offer...

Sometimes you hear something new and your perspective on music shifts seismically, making everything you were listening to previously sound safe and predictable by comparison. Inevitably, as one gets older and more musically knowledgeable, such moments are fewer and further between; either the shock of the new isn’t as high-voltage as it used to be, or it just irritates rather than stimulates. And so it was a pleasant surprise when, one morning – heralded by a storm of tape hiss and an enthusiastically bashed tribal drum – a new band called tUnE-yArDs (aka Merrill Garbus) came at me from the hi-fi speakers like a Dadaist, feminist pop warrior.

Be different - take a festival break in Europe instead of the UK, and catch a different landscape. While artists in both new music and classical are constantly circling the world in search of more picturesque settings, you can find your alternative Glasto in Denmark or Belgium, or you can find favourite chamber musicians in Austria rather than London. theartsdesk brings you listings of this year's major European festivals: rock in Sonar, Sziget and Stradbally, opera in Bayreuth, Verona and Salzburg, dance in Vienna, Epidauros and Spoleto, visual arts in Istanbul, Zurich and Avignon. This is the indispensable clickable guide to a cultured break in Europe.

Even the cover artwork refuses to conform, breaking the first rule of graphic design by utilising a dozen different typefaces and alternating upper and lower-case lettering for maximum optical anarchy. In fact, the inference is that we should play by Merril Garbus’s rules by typing “tUnE-YaRdS” rather than “Tune-Yards”. Such wilful solipsism could be interpreted as pretentiousness, but after several listens to this New England lass’s second album I’d be more than happy to write her band’s name in raspberry jam with my finger, if that was her wish.

At its best, and most preposterous, John Cage's work can be a mind-cleanser. The overwhelmingly silly randomised conjunctions and ontological punning of the great Zen master of the 20th-century avant-garde can coax and trick you into letting go of categories and judgments, scale and expectation, and just letting yourself get swept along with the gloriously complex and profoundly nonsensical multidimensional parlour games. Where some artworks might make you feel like you're on drugs, or

I can still remember the excitement of pounding the pavements of SoHo in the early 1970s. Nowadays, this part of downtown Manhattan is awash with expensive restaurants, boutiques and smart galleries, but then it was a scruffy industrial area of warehouses and sweatshops. The factories were closing and the container trucks leaving, though, and artists were gradually infiltrating and turning the huge empty spaces into studios where they often lived illicitly.

A maypole greets you on entry to the Serpentine Gallery; don’t expect a cheery celebration of spring, though. Nancy Spero’s installation Maypole: Take No Prisoners II (2008) is a scream of rage against violence and its hapless victims. Dangling from coloured ribbons, dozens of decapitated heads hang in the air like an explosion of shrapnel. Mouths gape open in pain and terror - or is it hatred? One can’t be sure, since some seem to be spitting venom from bloody tongues as though, even in their death throws, they are intent on spreading a gospel of vengeance and destruction.

The Detroit electro-techno duo of James Stinson and Gerald Donald aka Drexciya never gave away their secrets easily. Almost completely anonymous and never photographed during their 10-year existence – which ended with Stinson's 2002 death after a long illness – they surrounded their music with a complex mythos and mischievous wit comprehensible only to a small, obsessive cult audience. Only now are they getting wider appreciation, with a new generation of electronic musicians like Rustie hugely influenced by their sparse electronic funk, and the art world being introduced to their conceptualism via the work of the Turner Prize nominated Otolith Group.