Article: Adult contemporary R&B may be played on both soft AC stations and urban AC. It is a form of neo soul R&B that places emphasis on songcraft and sophistication. As the use of drum machines, synthesizers, and sequencers dominates R&B-rooted music, adult contemporary R&B tends to take most of its cues from the more refined strains of 1970s soul, such as smooth soul, Philly soul and quiet storm. Classic songwriting touches and organic-leaning instrumentation, often featuring string arrangements and horn charts, were constants.

Question: During what decade was smooth soul popular?
1970s