OAE / Rattle, Royal Festival Hall / Queen Elizabeth Hall, London

Sir Simon Rattle's returns to these shores to conduct the period-instrument line-up of the Orchestra of the Age of Enlightenment seem to be turning into major events, to judge from the packed houses for his latest pair of South Bank concerts, combining familiar Brahms with less familiar Schumann.

Admittedly, one might question how "historically informed" the performances really were. Would a Schumann symphony of c1840 have been given with as large a body of strings as a Brahms overture of 40 years later? How many orchestras of c1880, including a new-fangled valve tuba, would still be deploying a complete line-up of valve-less, essentially 18th-century horns? And would any 19th-century conductor - even Berlioz or Wagner at their most histrionic - have virtually ceased to beat time for bars on end while shaping phrasing in such extravagant parabolic gestures?

Sir Simon's underlying aim in this context would seem to be to restore, by whatever means, something of the freshness - strangeness, even - that such repertoire must have presented to its original audiences. His finely paced account of Brahms's Tragic Overture that opened the first concert in the Queen Elizabeth Hall, certainly reminded one that this least played of the composer's major orchestral works unfolds one of his most majestic structures and contains some of his most imaginative strokes of orchestration.

The two Schumann performances in this concert proved more variable. The Violin Concerto, his last major work before his mental collapse and subsequently suppressed by Clara Schumann, Joachim and Brahms, is problematic. Its opening tutti has a curiously incomplete quality, as though it were the harmony to a tune the composer forgot to add, while the finale interposes an arthritic polonaise rhythm with impossibly fast solo flurries. In the first two movements, Rattle and his sweet-toned, almost vibrato-less soloist Thomas Zehetmair nevertheless found out affecting moments of sentiment and time suspended - only to adopt so stolid a tempo in the finale as to subvert its character.

Sir Simon's approach to the original 1841 version of Schumann's Symphony No 4 in D minor proved equally extreme, with its first and last movement allegros launched at already cyclonic tempi which then accelerated still further: viscerally exciting, to be sure, and offering heightened contrasts with the work's slower sections, but one questioned the cost in scrambled detail. The two Schumann items which opened the second concert in the Royal Festival Hall were more equably done, however: the fine, if not quite top-drawer, overture to his opera Genoveva, and a late choral and orchestral setting of Hebbel's Nachtlied, full of characteristic dying falls and crepuscular textures, lacking only a memorable melodic line.

Those, though, were mere upbeats to what proved a revelatory account of Brahms's Ein Deutsches Requiem. Here Rattle's uncanny ability, as it were, to breathe structure in naturally unfolding spans when the heights and depths of his musicality are fully engaged came into its own. The grainy strings and pungent winds of the OAE truly served to clarify the richly Brahmsian textures that modern orchestras so often homogenise and clog up. Simon Halsey's expert training of his 44-member European Voices paid off in choral textures of immaculate balance and expressivity. With the soprano Susan Gritton exquisitely phrasing her "Ihr habt nun Traurigkeit" and intense, focused contributions by the German baritone Dietrich Henschel, this performance lacked only for sonorous bloom in the miserable RFH acoustic.