Velcro ties are good to clean up cords. Sound proofing is harder to do since it deals with a lot of variables but there are foam sound padding online. Just depends if youre trying to keep sound in or out. If you lmk a little more specific i can point you in a direction ✌🏼

I recommend XLR cords for Mics he might buy. External solid state drives are good for when he saves the large music files. A usb hub will be good for all the stuff he might have to plug into his computer. Those are just off the top of my head. Hope this helps 🤞🏽