Here are my guesses:

Jacqueline Du Pre: ESFp (though one could make a case for ENFp based on "negativism")
Daniel Barenboim: INTp (although the relationship wasn't perfect, he seemed to come off as an INTp, albeit a highly driven and confident one.)
Hilary: INFp (though not dual with Jackie, they had a very close relationship. It seems clear they were both Fs.)
Hilary's husband: ESTp (again, although it wasn't a problem-free relationship, he came off as ESTp)
Hilary's teacher: ENTj (seen through INFp perspective, not a full picture. ISTj also plausible.)