Appearances, they say, can be deceptive. The international festival opened with Gyorgy Kurtag's Stele and Janacek's Glagolitic Mass: both works ostensibly deal with ritual, though nothing in either is quite what it seems. Stele turns a colossal, post-Romantic orchestra into a chamber ensemble, as it explores the public and private memorials that resonate through time. Janacek, meanwhile, sets the Catholic Mass in old Slavonic. The God to whom it is addressed, far from being merciful, is a savage, pantheistic deity of exaltation and terror.

The two works were performed without an interval, although with different conductors. Garry Walker shaped and moulded Stele with tender reflectiveness. Lingering over Kurtag's precise yet probing sonorities, he achieved extraordinary things in the final section, in which vast slabs of sound seemed to hover and pulsate in the air.

Charles Mackerras, arguably today's finest Janacek interpreter, took over for the Glagolitic Mass, peeling away its Christian veneer to expose the pagan rawness beneath. The Edinburgh Festival Chorus responded to him, alternating raucous, animalistic cries with quiet murmurs of awe and fear. The abrasive playing of the Royal Scottish National Orchestra, all bellowing brass and heaving strings, was furious in its intensity, if occasionally suspect in intonation.

The soloists were variable, with Jane Irwin's hieratic mezzo balanced against Neal Davies's solemn, if underpowered bass. The tenor, Glenn Winslade, his voice heavily pressurised, belted a bit. Janacek wanted the crucial soprano solos to sound like "a maiden angel", although here we had the astonishing Christine Brewer, her great, voluptuous voice seemingly dredging primal emotions from the earth and flinging them exultantly towards heaven.