Family Search has a copy of his death certificate:https://familysearch.org/pal:/MM9.3.1/TH-267-11662-10022-51?...
place of death: Davidson Co., Civil Dist./1st, city/Nashville, TN
full name: John G. Miller
residence: 1213 Fatherland St.
male / white / married
wife: Minnie S...n Miller
age: 67 yrs., 11 mos., 25 days
date last worked: 8/3/1931
time spent in occupation: 50 yrs.
birthplace: York, PA
father: John G. Miller Jr.
father's birthplace: Germany
mother's maiden name: Christina Febry
mother's birthplace: Alsace Loraine
informant: T.K. Hobarn, Chattanoga, TN
burial: Mt. Olivet, 8/5/1931
undertaker: M.S. Combs & Co., Nashville, TN
filed 8/5/1931, Nora Hollister
death date: 8/3/1931
physician attended: 7/21/1931 - 7/29/1931
time of death: about 11:00 am
principal cause: chr. myocarditis
contributory cause: heart failure (sudden death)
disease/injury related to occupation: no
physician's signature: unclear
physician's address: Nashville, TN
Good luck with your search!