Complex sentence: In 2015 his rediscovery was sparked by the first release of a selection of his live performances and some modern-day commentators have also declared him one of the greatest pianists of all time.
Split into simpler sentences: In 2015 his rediscovery was sparked by the first release of a selection of his live performances. Based on these performances some modern-day commentators have also declared him one of the greatest pianists of all time.