Complex sentence: Albert played cornet in colliery bands, and taught Gracie to play the cornet at the age of 12; within two years she was playing in the Firbeck Colliery Band alongside her father.
Split into simpler sentences: Albert played cornet in colliery bands, and taught Gracie to play the cornet at the age of 12. Gracie played with local brass bands in her teens, including the Firbeck Colliery Band alongside her father.