According to Paul Bierley's biography of John Philip Sousa, "John Philip Sousa, American Phenomenon", several musicians who had played under Sousa attended the world premiere of the film but walked out in disgust.
Clifton Webb, who had starred in musicals on Broadway, had been offered the chance to appear with Fred Astaire in the MGM musical The Band Wagon (1953)--which is now considered one of the classics of the era--but passed it up to be in this film because his role of John Philip Sousa was the lead, whereas he would have only played a supporting role to Astaire in "The Band Wagon".
Sousa was superstitious and refused to wear a pair of gloves more than once considering it to be bad luck. In the beginning of the film he orders 110 dozen pairs of kid gloves (1320 pairs) at five dollars a pair. That comes to $6,600 at a time when a new car cost about $700 and you could buy a house for around $4000. Some biographical sources attribute his never wearing the same pair of gloves more than once, not so much to superstition, but to the white gloves getting stained easily by the ink of his music scores as he turned the pages and otherwise handled them during his concerts.
In supplemental material on the DVD they reveal that, while the story for the most part follows Sousa's autobiography, Willy Little and Lilly Becker never existed. They were written in to add a little love interest.
Meredith Willson, who went on to write the prize winning musical play and movie "The Music Man", toured as a musician with Sousa's band in the early 1920's.