On the other hand, if I recall correctly, yours is not the first mention of sibilance on Barbour LPs. So in this case, it might be the LP. Do you hear sibilance with other vocalists? I also doubt Patricia gets up to 3-4KHz ( per Mijo) in her vocal range.
Sibilance
Anyone else troubled by sibilance on Patricia Barber(IMPEX, 1STEP)) otherwise wonderful recording "NIGHTCLUB"?