Complex sentence: The lyrics stating "alleghenee, genec, genac, genac" reference the "Official University Yell" by 1891 graduate W. A. Johnston, that itself is referencing the Allegheny Mountains of Western Pennsylvania.
Split into simpler sentences: The lyrics stating "alleghenee, genec, genac, genac" reference the "Official University Yell" by 1891 graduate W. A. Johnston. The Yell itself is referencing the Allegheny Mountains of Western Pennsylvania.