Complex sentence: According to Basil Tschaikov, Karl Haas was a fine instrumentalist but a poor conductor, such that when playing the Richard Strauss Sonatina No 2 for the BBC on two occasions, the second was by far the better performance.
Split into simpler sentences: According to Basil Tschaikov, Karl Haas was a fine instrumentalist but a poor conductor. This was evidenced when playing the Richard Strauss Sonatina No 2 for the BBC on two occasions, as the second was by far the better performance.