Complex sentence: A number of their songs are accompanied with a dance routine, the most famous of which is their dance to the song "At The Ball, That's All" sung by The Avalon Boys in their 1937 film "Way Out West".
Split into simpler sentences: A number of their songs are accompanied with a dance routine. The most famous of which is their dance to the song "At The Ball, That's All" sung by The Avalon Boys in their 1937 film "Way Out West".