yes its corrupt but from this its an EASY fix:

Tried it, doesn´t work. The first byte of the file header isn´t there, that´s easy to fix.

Download this file:
http://home.arcor.de/gizzmoe/files/r.txt (Right-click, Save as)

Copy it into the same directory as the rar archive, then start cmd (command line), go to the directory where both files are and run this command:

copy /b r.txt+"Ultimate Gramophone Pack - 150+ tunes and broadcasts.rar" new.rar

Then unpack new.rar.