Your favourite music movie?

O Brother, Where Art Thou?

Streets of Fire

Amadeus
Immortal Beloved
Singin in the Rain
Paris Blues

and another vote for West Side Story

"The Wall".  It most strictly meets the original question as a Music Movie.  The music itself stands on its own as it was developed first and contains very little dialog.  It artistically mixes animation and live action and is enjoyable with eyes opened or closed.  The songs are meaningful and the movie is not filled with non-singing twittering about breakfast or a contrived transition to bridge memorable songs.

To me, "Tommy" contains too many elements of a musical and is better contexted as a true rock opera but not as cohesive when considered as stand-alone music.  There are far too many plot transition jingles/songs that only maintain their relevance in the context of the film....Tina Turner's Acid Queen and the injured glamour girl with the child Frankenstein guitarist on stage...as examples.

"Yellow Submarine" should not count but it is simply brilliant and a very stark contrast to the other Beatles movies which were more simply live documentaries masking their early explorations in drugs and religion...and drugs.  If only the world had more studio footage of the Beatles in action.

"West Side Story", "Grease" and even "The Rocky Horror Picture Show" were adaptations of musicals as well as "Sound of Music".  "Little Shop of Horrors" was well done also if you like that sort of thing, but still originally musicals.

"Spinal Tap" and "A Mighty Wind" are great musical mockumentaries.

"The Last Waltz" has Scorsese's involvement and reached a wider audience for that reason and the very special guests, but would not consider it a "movie".

"Frozen" and "Tarzan" (moreso Tarzan) have good soundtracks but so did "Snow White" and "Mary Poppins".

"Amadeus" +1 is beautiful.

Heavy Metal