The Torah mentions offerings that are voluntary, and that theoretically could come to include a burn-offering, but the Torah also specifies the burnt-offering so that the details of accompaniment are also learned (for example, the libations). And we see the halakhic hermeneutical principles of deriving the general, the specific, and the general -- which concludes with a narrower application that one might have thought. Also, the specifics of offerings that indeed involve accompaniments -