The all-Brahms concert began with the Academic Festival Overture. For me it's a familiar work, but yes, there was something extra to the performance, particularly in the contra-bassoon and timpani playing, and the unvalved horns. I found myself thinking of Jersey potatoes: period instruments make for a more earthy performance.
Next, a less familiar work, the Alto Rhapsody, with mezzo-soprano Jamie Barton and the men's voices of the Choir of the Enlightenment. Interestingly, the talk hadn't mentioned at all any changes in vocal or choral performance over time. I thought it was a very sympathetic performance of an engaging piece.
The final work of the first half was new to me, and a Proms premiere: Triumphlied. The baritone was Benjamin Appl, this time with the full choir. Though well performed, this felt a little out of character for Brahms; it was composed to celebrate victory in the Franco-Prussian war, and the unification of Germany, and was consciously modelled on works by Handel also celebrating military victories.
After the interval, the final scheduled work was the Symphony No. 1. Again it's a familiar piece for me, and so I was interested to see and hear the different approach of the orchestra. Controversially, in some circles at least, I was a bit surprised at the use of vibrato in the strings. There were a few interesting - and sudden - tempo changes, and one or two distinctive portmanteau effects (hints had been dropped about this in the talk). The programme notes pointed out the references to the other two "B"s - the opening of the symphony clearly has links to Bach's St Matthew Passion, and the main theme of the finale to Beethoven's Ode to Joy. I've often thought of the links between Brahms and Bach in general, taking just the right harmonic steps to modulate from one place to another, but once these links are pointed out, they seem so obvious. I thought it was a very successful performance, and I wasn't alone. I've been to a few concerts featuring Brahms, in which the conductor has eschewed the "obvious" choices of encore for something more out of the way; but in this "historically informed" performance, it was back to the staples, and we had the sparkling Hungarian Dance No. 21.