Complex sentence: Niccolò Paganini's cycle of 24 caprices, long considered impossible to perform, holds a special place in Kogan's repertoire, which comprises almost all great concertos for violin and orchestra.
Split into simpler sentences: Niccolò Paganini's cycle of 24 caprices that used to be long considered impossible to perform holds a special place in the violinist's repertoire. His repertoire comprises almost all great concertos for violin and orchestra.