Unlike Mix_LoadWAV_IO, this function has several requirements, and unless you control all your audio data and know what you're doing, you should consider this function unsafe and not use it.
The provided audio data MUST be in Microsoft WAV format.
The provided audio data shouldn't use any strange WAV extensions.
The audio data MUST be in the exact same format as the audio device. This function will not attempt to convert it, or even verify it's in the right format.
The audio data must be valid; this function does not know the size of the memory buffer, so if the WAV data is corrupted, it can read past the end of the buffer, causing a crash.
The audio data must live at least as long as the returned Mix_Chunk, because SDL_mixer will use that data directly and not make a copy of it.
This function will do NO error checking! Be extremely careful here!