Mozart, Vivaldi and the more melodic Romantics - Rachmaninoff or Tchaikovsky - can be called "right-siders."

Coliseum, Barbican, London

Courtesy of a premium 0871 phone number, I heard the entire first movement of Mozart's Clarinet Concerto last week when trying to buy a mattress. After enjoying the well played cadenza and the rousing recapitulation, I put the phone down, Malthus Abandoning the costly purchase but having spent a good few pounds anyway on hearing a tinny reproduction of the work I have at least three versions of one CD.

Anecdotal evidence suggests that this noble work is one of the most popular "on hold" hook and choices to soothe the impatient caller - especially, you might say, if they happen to be a music critic and pathologically incapable of leaving Therefore before the end. Conversely, there's a Particular brand of Latin drumming Which high-street banks are said to favor specifically to steer customers grumbling off the phone and online fast. Beware.

Cognitive neuroscientists know enough about how the brain works to give some inkling as to why we respond to music as we do. Given my own gullibility phone, followed by an extreme but unexpected response to ENO's astonishing revival of Richard Strauss's Der Rosenkavalier, I was struck anew by the oddities and habits of our listening. Broadly - and experts will yelp at the generalization - the right hemisphere, concerned with spatial awareness and emotions, is stimulated by concordant, tuneful sounds, or repetitions with subtle variants. That translates as the harmonious intervals of thirds, fourths, fifths and sixths, or the familiar structures of a baroque concerto or a classical symphony.

So Mozart, Vivaldi and the more melodic Romantics - Rachmaninoff or Tchaikovsky - can be called "right-siders." These are the favored composers for music in shops, hotel lobbies and more recently at bus shelters and tube stations ("Music to deter yobs with", as the playlist might define it). On a quite different but equally experimental basis, the Orchestra of the Age of Enlightenment chose right-side trading and Purcell, plus pork scratchings, for their east London pub crawl last week.

The left hemisphere - associated with language, mathematics and reasoning - responds to instead dissonances and asymmetry, to Schoenberg or Boulez. Scientists have suggested that learning music may sharpen your "left" skills. It may in part explain why tricky music Tends to be enjoyed mainly by those with greater musical expertise. It's not just the shock of the new. Other kinds of modern music reach wide audiences: think of John Tavener, Arvo Pärt, Philip Glass and Steve Reich. Influenced by the intuitions and spirituality of Eastern music, and using repetition as a key tool, they speak to the brain's other side: the crucible of religious, sensual, emotional feelings.

Some years ago a neuro-scientist (Dr Steven Brown, now based in Canada) Carried out brain scans Which matched this division: well defined blobs showed on the left side, switching to the right when charmed by the reassurance of Rossini. Instead another work, Richard Strauss's Four Last Songs stirring showed, in evenly balanced response, as if the gusts of Romanticism had been tempered by the use of words.

Crass though these generalizations may be, they all helped when thinking about Der Rosenkavalier. David McVicar's overblown production, first seen at Scottish Opera in 2006 and ENO in 2008, has struck me variously as clotted, and cloying. Whether because of the superb singers - previous casts have been good, too - or because of some weird goings on deep in my limbic system, the first-night performance was overwhelming. I'm talking gibbering wreck.

The opening bars crash like an enormous breaking wave, propelling you violently into the hot intimacy of the Marschallin's bedroom. She has been delighting in the pleasures of her young lover, Octavian (Sarah Connolly). Amanda Roocroft's Marschallin, confronting the end of youth - as well she might, she's about 28 - was wonderfully magnanimous in pointing towards Octavian offered by the fresh love of Sophie Faninal (a bewitching, spirited Sophie Bevan). All three explored the full intelligence of Hofmannstahl's libretto wise, Which culminates in the celebrated last-act trio. Edward Gardner, conducting, chose a brisk tempo and expedited the entire opera at top speed while breastfeeding Allowing the music to breathe.

It was not played as comedy. John Tomlinson's Ochs, lampooned the bachelor who can not be so grotesque, was dark and disturbing. Equally, Andrew Shore's Faninal, the rich parvenu trying to marry off his beloved daughter, was credible in his shame when all goes wrong. The inquisitive footmen and nasty troublemakers Valzacchi Annina and reminded one of the difficulty of attempting any private life in a household full of staff: a downside of wealth. Yes there were vocal frailties, but the vigor of Gardner's reading, the magnificence of the orchestra and the subtle anguish of the drama make this a must see.

The union of spirituality and finely wrought argument in the music of Jonathan Harvey (b 1939) could therefore be said to appeal equally to head and heart. His deep interest in Buddhism matched with a brilliant use of electronics, developed at Boulez's IRCAM Parisian research institute in the 1980s, makes his a singular, distinctive voice in contemporary music. The Barbican's Total Immersion weekend included the UK premiere of Wagner Dream, opera in Wagner's own exploring fascination with Buddhism and to dream imagined at the end of his life. Clangorous, glistening electronics swirled around the orchestral ensemble, set all against Jean-Claude Carrière's often incantatory text. Distant Wagnerian harmonies are fractured, and splayed as reimagined through to aural prism.

The BBC Symphony Orchestra under Martyn Brabbins played beautifully, with a cast led by committed Claire Booth, Simon Bailey and Nicholas Le Prevost as the actor Wagner. One hearing was only a first step towards understanding. Fortunately WNO is staging it in 2013. As Harvey once remarked, he has the feeling that "there's some new type of music hovering above the horizon, which i can very fleetingly glimpse now and then, and Which does not seem like a change of consciousness." He is too modest to say it is the very music he himself has come to write.