MUSIC / Out of the top drawer: Robert Maycock on rediscovered theatre pieces by Prokofiev and Franck and a surprise party from the Sudan

Was there ever a week like it for vocal discoveries? On Monday, at the Queen Elizabeth Hall, the Docklands Sinfonietta gave the first-ever full public performance of Prokofiev's music for Eugene Onegin, dovetailed smoothly into a translated adaptation of the Pushkin story. A long evening slipped by in no time as a state of steadily increasing enchantment took hold. One top-drawer Prokofiev melody followed another, romantic and piquant, sometimes familiar - he recycled some of the score into other works - and often completely fresh.

Little of it is actually sung; mostly the orchestra plays beneath, or between, the speeches and narrations. But it has the same gift for pinning down character in a phrase or a stroke of colour that distinguishes Prokofiev's ballets. Emerging from a state of deceptive tranquillity, it later comes to pace and punctuate the action with his usual sense of theatrical impact, and there are constant strokes to relish: the tunes that recur in ever-changing orchestrations, the dance episodes, the wit - one brief number, played first by a pair of harpsichords and then by a wind band, sets off overt laughter with its harmonic lurches.

All this brings out a satirical-comic edge in Pushkin that Tchaikovsky's opera sidelined. It does not plumb the loner's depths of despair in the same way, but in this performance it caught all the delicacy of sentiment with some sweet-toned string playing under the direction of Sir Edward Downes, the prime mover in the whole project. A cast of actors led by Timothy West read the text from scripts; this Onegin really needs a full staging to get round the inevitable stumbles and pedestrian half-acting that occur in concert conditions. In the meantime there is a recording on the way, made the next day.

The find of the week, though, was Cesar Franck's opera Hulda. When University College Opera chose it for this year's Bloomsbury Theatre season, they did not know it had never before been performed in its entirety. The composer never saw any of it. His son, in a well-meant attempt to get it put on somehow, allowed brutal cuts, and for the past century it has languished as 'evidence' that Franck wasn't cut out for the theatre. David Drummond, UCO's director of music, was fascinated enough to track down the original full score and let it speak for itself. The result puts hearsay thoroughly in its place.

It's true that Franck lacks flair for the episodes of violence, and with its unwieldy list of minor characters Hulda doesn't really achieve a dramatic balance. But it is beautifully composed and scored, and small moments of magic - a fading clarinet solo here, a quartet of saxophones there - crop up all the time. Drummond conducted with conviction, and the up-and-coming Adele Paxton brought eloquence and understanding to the magnificent title role at the heart of a fairly basic production in striking, Munch-style sets.

As for vocal surprise of the week, that has to be the opening concert of the 'New Visions of the Horn of Africa' season at the QEH last Saturday. We expected two Sudanese singers with oud, the Arab lute. We got them, but with a punchy, amplified band including violin and piano accordion, saxophone and guitars, keyboard and two drummers. Abdel Aziz El Mubarak delivered sophisticated, urban versions of his songs; Abdel Karim El Kabli found a purer, more freely expressive way.

The music itself, pentatonic and strongly African in its rhythms, sometimes sounds like Irish traditional music with swing. On Saturday the first half hovered on the brink of nightclub style, but the large audience loved the second, dancing in their seats and wandering down to pay their respects at the front. They had just about warmed up when the concert stopped and the hall shut down, leaving a sense of aimless frustration: a case of wrong venue if ever there was one.