Haydn said to Leopold Mozart one day : `` Before God and as an honest man I tell you that your son is the greatest composer known to me either in person or by name . He has taste , and what is more , the most profound knowledge of composition . '' Haydn in 1785 told the visiting Leopold : `` I tell you before God , and as an honest man , your son is the greatest composer known to me by person and repute , he has taste and what is more the greatest skill in composition . ''