After the Second World War, he returned to the German Folk Song Archive in 1946, where he worked as an archivist and head of the music department until 1958.
In his main work Die vier Weltalter der Musik Wiora gives an overall draft of music history.
Through the old Jewish texts and Synagogal Singing he draws conclusions about the even older musical cultures of the Sumerians, Babylonians and Mesopotamians.
He illuminates the unique theoretical penetration of the object in the disclosure of the laws of music, without displacing the natural through coercive orders.
In the fourth chapter on the world age of technology and global industrial culture he describes the conquest of "new territory" and the narrowing to the limits of music since the 19th century, for example in Max Reger and Claude Debussy.
Wiora approves of jazz more than a mixture of European harmonies and African rhythms and performance.