Both Gustav Mahler and today's original instrument practitioners recognized the same problem in big orchestra performances of Beethoven, but went about opposite directions for resolving that problem. I'll explain: as concert halls and orchestras continued to get bigger in the period spanning from the mid 19th century to the early 20th century, the proportion of strings to winds became ever more skewed. The original instrument claque have addressed this imbalance by cutting down on the number of strings, and generally performing/recording their Beethoven (and others) in smaller venues. They also employ authentic period wind instruments which typically have a less tame, more piercing tone quality than their large philharmonic counterparts. Add real calf skin heads on to the timpani, and you're off and running. Mahler, on the other hand, unabashedly adjusted his Beethoven to where in would sound good in the new and larger concert halls of his time. He also wanted to take advantage of the evolved improvements in wind instrument technology since Beethoven's time (that's to say nothing of pedal tuned timpani). Thus, in horn parts and trumpet parts, Mahler sometimes simply, 'filled in the dots' by putting in the notes within a scale that couldn't be played on the brass instruments of Beethoven's time (valves hadn't been invented or employed yet).
More to the point, Mahler adjusted the entire 'sound world' of Beethoven so that it would appear almost natural to audiences that were becoming ever more accustomed to Wagner and Brahms (to nothing of the future onslaught of Bruckner and Mahler's own music). One fault of this approach is that the music begins to sound a bit less like Beethoven, and a tad more like Mahler. That is to say, we don't recognize hearing the same-old Beethoven 9. What we hear, instead, is an 'updated' Beethoven with, in some instances, some very obvious improvements. The big climax of the first movement, for example, is more powerful yet clearer sounding under Mahler's retuschen (the German word for these adjustments). On the other hand, Mahler's trumpet doublings of some of the louder choral passages in the finale, seem a bit excessive. Yet, in the final analysis, we're left with a Beethoven experience that is both powerful in scope, and clear in texture (clarity meant almost everything to Mahler). Rather than reducing strings, Mahler brought his wind instruments up to four on a part (four oboes, four flutes, four clarinets, etc.). He also made Beethoven's timpani parts a bit more complicated - taking advantage of faster tuning via foot pedals.
This particular live performance took place in the famous Musikverein in Vienna. The Tonkunstler is generally considered to be the 4th place orchestra in Vienna, yet they play extremely well here. No doubt, everyone was enthused about taking on this Beethoven/Mahler joint venture. Tempi are generally quite fast, especially in the first three movements. As such, it's difficult to know if they were taken from Mahler's own markings, or if conductor Kristjan Jarvi has simply been influenced by the before-mentioned period instrument folks (that's to say nothing about the endless debates over Beethoven's own metronome markings).
The first movement is both rhythmic and hard driven, with one heck of a climactic passage (as mentioned previously). The scherzo is about as fast and 'demonic' as I've ever heard it. Again, some of Mahler's minor doublings seem a bit unnecessary, but everything is as clear as a bell. Clocking in at just over 12 minutes, the slow movement flows more like a natural stream, and feels less like an endless contemplation than usual (good horn solos too). The finale gets off to a bit of an odd sounding start, with Mahler doubling Beethoven's denuded double basses with celli. But, once our quartet of soloists arrive on the scene, they sound quite good together. That said, the tenor isn't the best when we get to his solo later on (I don't have his name with me right now). However, we get distracted to this fact by way of Mahler's biggest and most fascinating alteration: during the 'Turkish March', Mahler has the cymbals and bass drum played from offstage. Thus, he's able to make a big crescendo over the course of this charming march, without also having the percussion blow us out of the room by the end of it. It's a brilliant stroke that really works!
Whether any of this whets your appetite or not might, your judgment might get tilted by one additional fact: the recorded sound on the disc is excellent (the label is Preiser). It's not clear to me if the recording was made by the ORF (Austrian Radio) or not. If so, it's the best live sound I've ever heard come from those engineers ever (they're generally not so great). As an additional note, it's interesting to know that back in Mahler's time - while the newspaper critics hated (and greatly exaggerated) what Mahler had done with Beethoven - his Viennese audiences were completely won over. Just judging from the cheers and applause at the end of this performance, it sounds as though they've been won over again.
http://www.amazon.com/gp/product/B002UCTA98/ref=cm_cr_mts_prod_img