Complex sentence: Osborn said he was initially disappointed that Fender had not sent him a Fender Precision Bass, which he had been using, but he said he grew to like the Jazz Bass because the narrower neck made it easier for his short fingers.
Split into simpler sentences: Osborn said he was initially disappointed that Fender had not sent a Precision model, which he had been using. But he said he grew to like the Jazz Bass because the narrower neck made it easier for his short fingers.