Prom 32 featured two works written in the same year, 1878, by composers who worked mainly in the same city, Vienna. Brahms was an established composer when he wrote his Violin Concerto for his virtuoso friend Joseph Joachim, while Mahler was just 17 when he started writing Das klagende Lied for a competition (the version played tonight was completed in 1880). Both works can be classed as "late romantic", but they could hardly be more different: the Brahms is formal and elegant, thoroughly within its classical tradition, while the Mahler is packed with different themes and textures, groundbreaking and epic in scale.

Conductor Edward Gardner is more usually found in the orchestra pit of opera houses than on the concert podium, but you wouldn't have known it from his performance of the Brahms. I've heard him many times before but never seen more than the back of his head, and it was striking to see the way in which he exerted fine control over every detail, frequently changing his focus between orchestra members and marking his intentions precisely. The result was pin-point accuracy, an immaculate balance of timbre and phrases that were polished and perfectly weighted. The woodwind players in particular seemed to revel in it: the marvellous oboe solo at the beginning of the Adagio soared through the hall. Soloist Christian Tetzlaff also turned in an extraordinary performance. The Brahms concerto is supposed to be one of the hardest in the repertoire with its complicated, shifting phrasing and a ferocious array of double and triple stops. Tetzlaff made it look like a walk in the park: violinists in the audience were watching in awe at his formidable technique.

I feel mean to say it, but it was almost too good. There's an oft-repeated gag that the work is a "concerto for violin against orchestra:" Tetzlaff was so technically fluent that there was barely a contest. The result was a classically near-perfect performance of great elegance and beauty, but I missed that last edge of excitement of a virtuoso playing at the edge of the possible.

Tetzlaff gave us a lovely treat for an encore, playing the Gavotte from Bach's E major Violin Partita as a light hearted dance: lilting, effortless and delightful.

Das klagende Lied (usually translated "Song of Lamentation") is a work on an altogether grander scale, with a huge on-stage orchestra, a second orchestra off-stage, SATB soloists and a full choir augmented by a small children's choir. The words are written by Mahler in the form of a mediaeval ballad about a pair of brothers who compete for the love of a queen: one murders the other, whose bone is made into a flute which sings his lament when played. The story unfolds in around an hour of music, with different combinations of voices telling the story, interspersed with orchestral passages of varying length. It's a quite remarkable work in several ways.

While early Beethoven sounds a bit like Mozart and early Brahms sounds a bit like Beethoven, Das klagende Lied is unmistakably Mahler, whose musical style seems to have emerged from the womb fully formed. Many of his trademarks are clearly audible (the multiple rhythms, the little brass and woodwind quotes, the ländler, the slightly military brass), and it's hard to imagine another 17-year-old composer who would have calmly scored a piece for quite so large an orchestra.

But the most remarkable thing is the way Mahler generates excitement and epic narrative. The raw essence of the mediaeval folk ballad is massively amplified and enhanced, but retains its fairy-tale like ability to keep you engaged and wanting to hear what happens next (the Proms helped us by publishing the words in the programme accompanied by an excellent blank verse translation by Eric Mason). Mahler knew exactly why he wanted from that enormous orchestra: it's used to generate contrast and dynamics, so that the climaxes hit you like thunderclaps and contrast beautifully with the slow laments or the more cheerful interludes.

I couldn't have asked for a better performance. The BBC Singers were in fine voice, and the orchestra gave us an extraordinary range of colours and textures. When the off-stage band came in for the first time, high in the balcony, there was an audible gasp from the audience, thrilled at the interplay between the two orchestras. The small group of boy trebles were clear and lofty, and the BBC assembled an all-star cast of soloists: Anna Larsson particularly shone as she provided the calming meditative foil to Melanie Diener's driving of the narrative. The tenor and baritone parts are a little less notable (both are mainly used in very short bursts), but Christopher Purves and Stuart Skelton both have wonderful voices able to fill the Albert Hall.

What impressed most was the clarity achieved by Gardner. Mahler's works of this scale are continually filled by several things happening simultaneously, and it's wonderful to be able to hear and distinguish them all without a trace of confusion or muddiness. Das klagende Lied is a work you need to see in the concert hall: I've listened to it on CD before and simply didn't get the same impact. This Prom was a fabulous introduction to a thrilling piece of music.