Complex sentence: He has been singing since the age of eight but did not pursue a serious profession in music until the age of 20 while auditioning for American Idol in 2007 and The Voice in 2011.
Split into simpler sentences: He has been singing since the age of eight, but did not pursue a serious profession in music until the age of 20. He auditioned for American Idol in 2007 and The Voice in 2011.