Complex sentence: He was also the first MGM lion to roar; his roar was first heard via a gramophone record on MGM's first sound production, "White Shadows in the South Seas" (1928).
Split into simpler sentences: He was also the first MGM lion to roar, which was first heard via a gramophone record. This was done for MGM's first sound production, "White Shadows in the South Seas" (1928).