The Historic Two Year Recording Ban
For two full years, union musicians were strictly forbidden from entering recording studios. This unprecedented strike silenced the music industry, leaving labels unable to record new instrumental tracks.
During this massive standoff, artists could still perform live on the radio but were banned from making records to demand better royalty payments. Because they couldn't hire instrumentalists, record companies were forced to release vocal-only tracks featuring choir accompaniment. This shift unintentionally helped launch the solo pop star era, as singers became the focus of the music industry. It remains the longest and most impactful strike in the history of entertainment.
Source: 1942–1944 musicians' strike