I'm writing a piece where the beginning and end use the damper pedal only, and the middle uses sostenuto only. Currently these are notated with con ped. and con sost., but I wonder if that might create confusion for a performer who might try to use both at once. Is this likely to be confusing? If so, what's the best way to make it clear?
When a new pedal indication is encountered, it is assumed to cancel the previous one. In a score indicating "con ped." followed later by "con sost.", the "con ped." remains in effect until it is replaced by "con sost." — and vice versa. If two pedals are to be used simultaneously, that would be explicitly notated. (Also, with damper and sostenuto pedals specifically, it would not make sense to use both together. The damper pedal overrules the sostenuto.)