Toscanini was famous for claiming to adhere strictly to the score, avoiding any modification of what the composer had written, but a friend once proved to him that he was in fact making slight nuances. Toscanini admitted this saying “one cannot be a machine”.
If you play music exactly as written it sounds dull and dead. In particular a slight rubato, an almost imperceptible constant varying of the timing from beat to beat, is necessary.
The greatest interpreters are those who seem to do this so naturally that an innocent listener often doesn’t seem to notice it outwardly, though they feel inwardly that the performance is somehow more alive. Elgar in particular was famous for doing this, and in his recordings, very often he doesn’t follow the score exactly.
I read an interview with Sir Andrew Davies around the time he was embarking on recording his Vaughan Williams symphony cycle in which, inter alia, he criticized Sir John Barbirolli for “stopping to smell the flowers along the way”. That immediately rang alarm bells, since I’d always considered Barbirolli to be a glorious interpreter of RVW’s music (as indeed did the composer himself). More than once I’ve pointed out that I find listening to Sir Andrew Davies’s performances rather like driving on a motorway from London to Edinburgh: we get on at the beginning and arrive at the destination at the allotted time, but with very little sense of any landmarks along the way.
If you listen very carefully to a really convincing performance of, say, Beethoven or Stravinsky, even one which respects the score in detail, you’ll find minute variations in speed, rhythm and dynamics not marked in the score, and it’s those that give the music life and make a performance one to listen to again and again with pleasure.
What marks out those conductors who successfully build climaxes is surely their ongoing attention to detail, and the realization that these things don’t just happen, but need something to grow from. If the way isn’t properly prepared, then the likelihood is that the moment will seem imposed, or worse still, underwhelming.
Knowing exactly where the climax comes is in itself certainly not a universal talent: even more interestingly, though, different conductors may find unorthodox places for the peak, and still be persuasive (Sir Charles Mackerras in the first movement of Walton’s Symphony No. 1 is an example which springs immediately to mind).