A search for renewals in periodicals was done for the years 1976 and 1977. There was no information on Metronome. The magazine appears to have started renewing copyrights for its back issues beginning in 1952, according to information located at copyright.gov. There's no evidence of a continuing claim on this material.
Note that it may still be copyrighted in jurisdictions that do not apply the rule of the shorter term for US works (depending on the date of the author's death), such as Canada (70 years p.m.a.), Mainland China (50 years p.m.a., not Hong Kong or Macao), Germany (70 years p.m.a.), Mexico (100 years p.m.a.), Switzerland (70 years p.m.a.), and other countries with individual treaties.
{{Information |Description=Cover of en:Metronome magazine for September 1949 with Artie Shaw on the cover. |Source=[http://www.ebay.com/itm/METRONOME-Artie-Shaw-Duke-Ellington-Guy-Lombardo-Louis-Armstrong-9-1949-/390689758085?pt=Magazines&hash=ite...