There are several definitions for 上. One is with a neutral tone : [shang] n. (after a noun) on, in, at, above, indicating an aspect; (after a verb, indicating) upward, an amount, a result, begin and continue doing...
but on audio I heard shang4 same tone as for other definitions. Is there an error on the audio or in the tone ?
Shang should always be a 4th tone as far as I know. As for the different meanings of the word, this is a common aspect of the Chinese language. Consider for example this humorous sentence using shang: 我爱上一个人。How many different meanings can you find?