I don't believe anyone is claiming, "audio grade", in reference to their diodes.
However: a number of gear manufacturers offer fast/soft recovery diodes (FRED/HEXFRED, etc) as upgrades to their equipment.
Personally (since their appearance in the marketplace): I've been upgrading my own equipment, as well as numerous others', with them and we've (invariably) enjoyed the benefit of improved presentation.
Caveat: Schottkys can appear tempting, but- can end up noisy in some audio circuits.
Ignore any that claim changes in rectification isn't/shouldn't/can't be audible.
ie: https://www.partsconnexion.com/diodes-rectifiers.html