Complex sentence: Smith's most widely known song is "Because the Night", which was co-written with Bruce Springsteen and reached number 13 on the "Billboard" Hot 100 chart in 1978.
Split into simpler sentences: Smith's most widely known song is "Because the Night", which was co-written with Bruce Springsteen. The song reached number 13 on the "Billboard" Hot 100 chart in 1978.