Complex sentence: Vogl continued to sing Schubert's music after the death of his friend in 1828, famously singing a complete performance of "Winterreise" shortly before his own death on the twelfth anniversary of the death of his friend.
Split into simpler sentences: Vogl continued to sing Schubert's music after the death of his friend in 1828, famously singing a complete performance of "Winterreise" shortly before his own death. He died on the twelfth anniversary of the death of his friend.