Use mt manager to open the Minecraft installation package and then check the Minecraft music package on Baidu. After you find it, it should be a compressed file, which defaults to the original BGM. If you want to change it, just unzip it and change it yourself. When saving, the format must be correct. Then unzip the saved compressed package into the Minecraft installation package using mt. Then your Minecraft will increase in size by about 60 MB. You can play and listen at the same time.