Beethoven's music in general, and the Fourth Piano Concerto in particular, is on the cusp between the Classical and the Romantic: the Classical forms are stretched to their limit but left unbroken, while Beethoven provides plenty of opportunity for a Romantically-minded interpreter to charge off in any number of wild directions. In the first half of last night's Prom, Murray Perahia and the Vienna Philharmonic gave us a performance very much towards the Classical end of the spectrum, with a sound fascinatingly different from many Beethoven interpretations.

I've admired Perahia's records for several decades, but last night's Prom was the first time I've heard the man in the flesh. Inevitably, I was apprehensive: Perahia is a great master of the keyboard, but he is known as a consummate recording artist rather than as an assured live performer. Any doubts I had were comprehensively laid to rest.

Perahia kept his tempi very strict, with a bare minimum of rubato. But this was in no way a robotic or metronomic performance: rather, the interest came more from the dynamics and articulation of the notes and less from pulling around of the rhythm. In those Beethoven phrases where the melody rolls upwards, all the mid-range notes which follow the melody came out with total clarity, making thorough musical sense out of what is often a mere wash of sound. When Beethoven increases the number of notes in a bar, Perahia kept right on the beat and gave us immense dynamic variation, so that the sound was thickened and excitement added while maintaining the underlying pulse of the music.

Bernard Haitink and the Vienna Philharmonic Orchestra produced the sort of classic orchestral sound that I grew up with. With no concessions to period delicacy, this was a big, rounded, blended sound whose effect was gorgeousness of overall timbre rather than expression of individual instruments. They play so tightly together that I often had the sensation of listening to an organ rather than to a group of seventy or so musicians. Taken as a whole, it was a rather reverential performance: no sweeping Romantic gestures and little of the impish humour that can be imparted to the rondo finale, but every note was in place, with the structure of Beethoven's composition clear and easy to follow.

The second (considerably longer) half of the concert was Bruckner's unfinished Symphony no. 9, played here in its three movement form without any of the various attempts at a reconstructed finale. Here, an enlarged orchestra produced a more open sound. The first movement comes in waves of sound where the crests are laden with brass, interspersed with troughs of more reflective string playing. The seventeen piece brass section were particularly prominent, seated in two rows high above the rest of the orchestra, and woodwind solos were clear against the string background.

For all the Vienna Philharmonic's wonderful tone and precise delivery, the first movement felt a shade restrained. Haitink's conducting was economical, with just a brief wave of the baton here and there: he gave the impression of a man confident in his players and content to let them do their job. And yet, without Haitink giving the appearance of having done anything about it, the sound became thicker and more potent at each wave. As we moved on to the powerful accenting of the second movement scherzo, the orchestra steadily increased in intensity, and the fast trio section was exciting, if not quite as manic as it is often played. This wasn't a mannered or overtly Romantic performance, but one which built steadily as the work progressed. By the time we reached the third movement adagio, the intensity had reached a high level and the lustrous string sound came to the fore, with the brass fanfares swelling the piece with profound nostalgia. As the gentle string sound faded gently away, we could be deeply satisfied by what we had heard while still wishing that there was a finale to come.

Without any attempt to overplay the Romanticism, Haitink and the Vienna Philharmonic gave us an hour of Bruckner's music in which they produced a consistently wonderful sound and steadily built up the emotional content of the work. It proved that there are many ways to approach Bruckner.