I love Fiona Apple’s work for many reasons. Primary among them is her voice. And not just the quality of her voice (which, she’d be the first to admit, is not technically perfect) but the way she uses it to convey the passion and pathos in her songs.
I also love her choice of instrumentation. The production on her albums is top-notch and she always manages to surround her piano with strings, horns, interesting percussion… all kinds of sonic goodies that feel somehow old-fashioned and ahead of their time all at once. Jon Brion deserves a lot of that credit, I think, but he’s actually produced only one of her three albums and they all share a similar vibe.