No offence mate, but frankly I cannot grasp what it is about your style of writing that takes a giant paragraph to say what can be summarised in about two sentences. 
No offence taken, "mate"(?!), but maybe you should just try that little bit harder - or maybe you should yourself "summarise" (was I intending in any case to "summarise? - this is your term, not mine)
1. the comparison with Kreisler and Oistrakh
2. Heifetz the pianist, especially after he ceased public violin playing
3. Heifetz's masterclasses
4. Rubinstein's opinion
5. The emotional power of Heifetz's violin playing
6. The effect of Heifetz's playing on me in my early days as a composer
7. The comparison with Michelangeli
8. The fact of Michelangeli's and Alkan's youthful prowess as violinists
and decide how many sentences you might sensibly require in order to do this. Of course, I could have split what I wrote into several paragraphs, but that's another matter...
Best,
Alistair