Complex sentence: Unmeasured preludes flourished into full-fledged compositions by the middle of the 17th century, however the development of lute music has already stopped by that time and the last surviving unmeasured lute preludes date from the end of the same century.
Split into simpler sentences: Unmeasured preludes flourished into full-fledged compositions by the middle of the 17th century. However the development of lute music had already stopped by that time and the last surviving unmeasured lute preludes date from the end of the same century.