A yid rocker
Oi Vai is yiddish slang for Dear Me! Its an expression of surprise (or dismay) or delight (or hurt): like what happens when you listen to this song
The melody is pentatonic (5 notes used out of the 12 available). The notes are 1, 4, 5, 9 and 10. These notes have been used many times before in many different ways, Ian Carrs Nucleus did a good version in 1970 interpreting it as a Balinese scale on Elastic Rock
The song was developed by changing the starting point of the melody and combining the altered melodies to create interesting harmonies
Oi Vai indeed!