It would be WRONG to say that Notes are the building block of music, as music being natural and continuous, logically or intuitively doesn’t seem to be constrained by few notes!
Any area of study is typically structured and broken down in s systematic & sequential fashion just in order to facilitate the easy understanding of the naturally occurring & more complex phenomenon & so is the case with music.
In music, a note is the pitch and duration of a sound, and also its representation in musical notation (♪, ♩). Notes are the building blocks of much written music.
A note gets it pitch by the frequencies of sound vibrations present in it basis the instrument or source it was derived from.
Two notes with fundamental frequencies in a ratio equal to any integer power of two (e.g., half, twice, or four times) are perceived as very similar. Because of that, all notes with these kinds of relations can be grouped under the same pitch class.
In traditional music theory, most countries in the world use the naming convention Do–Re–Mi–Fa–Sol–La–Si, including for instance Italy, Portugal, Spain, France, Romania, most Latin American countries, Greece, Bulgaria, Turkey, Russia, and all the Arabic-speaking or Persian-speaking countries. However, within the English-speaking and Dutch-speaking world, pitch classes are typically represented by the first seven letters of the Latin alphabet (A, B, C, D, E, F and G). A few European countries, including Germany, adopt an almost identical notation, in which H substitutes for B (see below for details). In Indian music the Sanskrit names Sa-Re-Ga-Ma-Pa-Dha-Ni is used, as in Telugu Sa-Re-Ga-Ma-Pa-Da-Ni (స రి గ మ ప ద ని), and in Tamil (ச-ரி-க-ம-ப-த-நி) Byzantium used the names pa-vu-ga-di-ke-zo-ni.