What is the meaning of 五音?

the five notes of the Chinese pentatonic scale (, , , , , also called , , , , after the Tang dynasty, equivalent to do, re, mi, sol, la in the Western solfège system or 1, 2, 3, 5, 6 in the Chinese numbered musical notation system)

the five classes of initial consonants of Chinese phonetics (喉音, 舌音, 齒音, 唇音, 牙音)

Source: wiktionary.org