You don't need a brain chip to send music directly to someone's brain, it can already be done with digitally modulated square waves sent to 2 probes that just touch the skin. The more advanced version can transmit the square-waves wirelessly, a radiowave signal. The brain can be accessed wirelessly like a laptop computer with wifi. 

Putting a "brain chip" on the brain to stream sound into it the audio cortex would be like taking apart a computer to try to access its audio circuit on the motherboard by connecting electrical leads to only the soundcard audio circuit when all you need to do is access the computer's wifi card wirelessly to gain access to the whole computer system, without having to disassemble, find, & probe individual circuits on the computer motherboard (the brain; Central Nervous System (CNS)), in this case (Elon Musk’s Auditory Neurolink), the sound card with the microphone input circuit (the audio cortex). 

By wirelessly connecting to the system's wifi card (the brain’s biological wifi circuit) you gain access to the complete operating system, the Central Nervous System (CNS), which has access to all circuits & peripherals at once (audio input/output circuit; video circuit; camera circuit; hard drive, memory, software, firmware), you don't need to take the computer apart to access/use it. You don't need to cut someone's skull open to gain access to the brains operating system, it can be done wirelessly. Once access is gained to the brain's operating system, the wireless user can access all the brain's peripherals/sensory & motor functions: auditory cortex (ears/sound), visual cortex (eyes/sight), olfactory cortex (smell), parietal lobe (spatial relationships; pain & touch), memory, Amygdala, hypothalamus (emotion chemical factory), thoughts, consciousness, 

Below: Google Docs Version