[AbdesSalaam Attar, Perfumer Composer]

If your demand is about Hyraceum, yes it is a base note.
About fixatives it is just a myth invented by perfumers in order to confuse people. No ingredient has the power to give lenght to a composition but some ingredients have the property to potentialize and fuse together other essences.

AbdesSalaam Attar
Compositore Profumiere