Jazz music played with piano with a 2/4 rhythm and with unexpected stresses in the music which make it irregular in some way. It was first composed by Scott Joplin in 1899, and it was very popular during the first years of the 20th century.
Now, I had never heard of rag music myself, but I had heard the melodies!
–Maple Leaf Rag (Scott Joplin)
– Pineapple rag (Scott Joplin)
– The Entertainer (Scott Joplin)