Complex sentence: In June 1965, their song "The Sound of Silence" was overdubbed, adding electric guitar and a drumkit to the original 1964 recording, this overdub was played widely on U.S. AM radio in 1965, reaching number one on the "Billboard" Hot 100.
Split into simpler sentences: In June 1965, their song "The Sound of Silence" was overdubbed, adding electric guitar and a drumkit to the original 1964 recording. This later version became a major U.S. AM radio hit in 1965, reaching number one on the "Billboard" Hot 100.