Complex sentence: At this time, Alan's eclectic approach to music was very new and hazardous, but it soon became popular, and over 1,500.000 records of that concert ("A l'Olympia") were sold.
Split into simpler sentences: At this time, Stivell's eclectic approach to music was very new and was considered risky, but it soon became popular. Over 1,500.000 records of that concert ("A l'Olympia") were sold.