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.

Who could not love Martin Creed? The tweed-encased harumphers of the world adore him, because they can say, “That’s not art,” and, “My cat could do that,” and have an all-round wonderful time. Conceptualists have it easy: what could be more fun than his Turner Prize-winning Work No 227, a light going on and off in a room? And lovers of abstract art love him because his work is just there. “Take it or leave it,” it seems to say. And they love him because, well, because his work is lovable.

Well, we all make mistakes. Or, in my case, we (I mean “I”) sometimes just fail to look. This new, small but perfectly formed exhibition of Bridget Riley’s work in the National Gallery’s Sunley Rooms follows the pattern that the gallery has developed over the years, with a single artist entering into a conversation with the great art of the past. Riley’s conversation is gripping, and one of the things it says (to me) is, “Shame on you for not looking.”

Tonight the company dedicated to the greatest radical of modern dance, Merce Cunningham, opens its farewell tour to London, a valedictory odyssey that will end next year. Last year Cunningham died, aged 90. He had just premiered a work called Nearly Ninety, and this is fittingly the last thing we will see of his company as it blazes one final circuit before closing down in December 2011.