Hi pax
from a purely subjective point I would suggest blending the filter signal with the original sound, because solo acoustic instruments each have their own unique timbral character, and filtering will make them sound ‘unnatural’; try cutting a band/region with a high Q factor and automating a sweep; also try the fixed-filterbank object, [ffb~ 4] referring to its helpfile for usage tips.

As most filters are essentially just sophisticated delay loop systems, also try the [tapin~]/[tapout] objects, with small delay times c.5-30ms for some filter-y/phase-y sounds.

HTH
Brendan

In my own experience, simple filtering doesn’t get you far on simple clarinet sounds (a clarinet spectrum is already a filtered one, in a way). More satisfying to alter the sound in other ways, or to filter a rich clarinet sound (multiphonics…)