Complex sentence: Vikernes began making music in 1988, but it was not until 1991 that he recorded his first demos as Burzum, while the first four albums were recorded between January 1992 and March 1993.
Split into simpler sentences: Vikernes began making music in 1988, but it was not until 1991 that he recorded his first demos as Burzum. Vikernes recorded the first four Burzum albums between January 1992 and March 1993.