Maybe it's the warm weather or an abundance of frenetic exhibitions, but recently I've been enjoying opportunities to visit art shows that are coolly poetic as a chilled glass of water. Roni Horn's exhibition at Tate Modern is perfect for days like these, littered with references to water in all its forms. In Still Water (The River Thames, for Example), which dates from 1999, Horn treats large close-up images of water as though they are topographical maps, picking out numbered areas in footnotes to describe her thoughts on this magical, mutable substance. Between the two thin sheets of gold foil laid one on top of the other in the sculpture Paired Gold Mats, for Ross and Felix (1994–95), shines a warm gleam of golden light, hinting at the otherworldly magic that lies within.  A group exhibition elsewhere in London, at Stuart Shave/Modern Art in Fitzrovia, is another reminder that many artists make things because it allows them to speak in a way others can understand. The Actuality of the Idea is a group exhibition of ideas and attitudes becoming form, including a brick sculpture from Carl Andre and Leonor Antunes's MMM (2008), a ragged, wandering assemblage of brass triangles and black rope that appears to have broken out of a wire fence. There is also a surprisingly colourful new piece from Rachel Whiteread, resinous blocks reminiscent of soaps or turkish delight stacked on a shelf.  If you need soothing in Milton Keynes, then spend a while with the work of the late James Lee Byers, who has been called a "homeopathic" artist – one who sought to alter the world through tiny acts. Byars let a single drop of perfume evaporate as an artwork, and was even once arrested for whispering in strangers' ears. This nomadic character became increasingly obsessed with a search for perfection. At Milton Keynes Gallery you can see many of these sensuous objects, made from gold leaf and roses, as well as Byars's circular letters and marble one page "books" – large circular tablets engraved with short phrases.  If this all sounds a little too quiet, those in Sheffield can ramp up the volume at Sound Spill at S1 ArtSpace. As the curators point out, not much attention is normally paid to the impact of noisy artworks except when attempting to minimise disturbance. So they have gathered together four works that include sound elements, which together create one sound piece. We have Richard Sides on rhythm, whose sculpture of glass panes includes devices which tap the glass; Nina Canell's woodwind video work, featuring a saxophone stuck in a tree; and Guy Sherwin attempting to recreate the soundtrack of the film Night Train. Completing the quartet is Torsten Lauschmann, whose sculpture of an overturned organ resting on two £10 notes plays a sustained chord, and throws puddle-like shadows in which animated numbers dance about.  It's your last chance to see Steve McQueen's Queen and Country at Middlesborough's MIMA, before the artist represents Britain at the Venice Biennale in June. McQueen has created postage stamp designs featuring a picture of every man or woman who has died fighting in Iraq, chosen by their families. Each sheet of stamps is displayed in a vertical drawer in a large oak cabinet. While the empty, waiting drawers might leave you with a chill, McQueen views the work as incomplete until issued as real stamps by Royal Mail. Why not sign The Art Fund's petition to have this done?
Laura McLean-Ferris: Roni Horn offers refuge at Tate Modern, James Lee Byars's sensuous objects go on show in Milton Keynes and four sound installations become one in Sheffield