Is it infringement to add background music to the video?

If it is commercialized, it is infringement and it is profitable. Pay attention to profit, not profit.

Generally, submitting to the video portal is considered as a "profit-making" behavior, and you can consult the customer service of major video websites for details.

Network infringement refers to the infringement that occurs in the network environment and is a form of knowledge infringement. Internet infringement is essentially the same as traditional infringement, that is, the behavior that the actor should bear civil liability according to law because of his fault infringing on the property and personal rights of others, and other damage behaviors that should bear civil liability according to the special provisions of the law.

Network infringement, as its name implies, refers to the infringement that occurs in the network environment. The so-called network refers to "a system that connects multiple computer systems with different geographical locations and independent functions through communication equipment and lines, and realizes resource sharing in the network with perfect network software (namely, network communication protocol, information exchange mode and network operating system)."