Hmmm..... I can't quite see how separate hits by "The Osmonds", "Donny Osmond", "Donny & Marie Osmond" and "Little Jimmy Osmond" can (according to the link) count as 'one artist'.
However, Mud, Alvin Stardust and The Bay City Rollers all had four Top 40 singles in '74 - Mud having two No.1 singles.
Meanwhile, Slade, the Official Greatest Band of 1974 (at least, according to The Big Brachiopod Book of Hit Singles) had only three Top 40 hits. :o(