When The Saints has a Verse as well as the familiar Chorus. The two are similar; but I shall concentrate on the Chorus.
There are three reasons why it is easy for the audience and lends itself to audience participation. (1) It has a simple 16-bar structure; (2) it offers a singer and echoing chorus possibility (Oh when the saints [Oh when the saints…]); and (3) it is repetitive: there’s nothing much to learn.
But they are also three reasons why the musicians do not much care for it: the tune poses no great challenge.
That is its simple chord structure (without any sophistication).
Note how you can get away with using just three chords: it is what musicians call a three-chord trick. The chords are the most common: the tonic, the dominant and the sub-dominant.
It is believed that this tune is a traditional gospel number dating back to the earliest days of jazz (and jazz funerals) in New Orleans. I am surprised, though, that not one of the early jazz bands - all through the great New Orleans and Chicago eras - ever seems to have recorded it. The only early recordings of When The Saints (dating from the 1920s), are by gospel singers and by singer-guitarist Blind Willie Davis (about whom almost nothing is known). You can listen to his performance by clicking here.
Some scholarly types claim the song was written in 1896 by James M. Black (1856-1938) and Katherine E. Purvis, who died in 1909. They were members of the Methodist Episcopal Church in Pennsylvania. But the song they wrote was actually When The Saints Are Marching In and it has a different melody. I have examined the sheet music.
When The Saints Go Marching In was used in the 1936 film Green Pastures, for which it was claimed that Virgil Stamps wrote the music. It was even copyrighted in 1937 by Virgil Stamps, with words by Luther G. Presley. Stamps was born in Texas in 1892. He got a job with The Tennessee Music Company and started composing songs by 1915. He was also a singer and a keen student and proponent of gospel music. So it is conceivable that he really did compose it in his younger days. Later he had his own music company. He and his singing quartet became early stars of the radio age. Luther Presley, whose name also appeared on the copyright and who may or may not have written the words, died in 1974, having lived to the good old age of 87; so he at least knew what world-wide fame the song went on to achieve.
Incidentally, I received an email in May 2015 from the great-niece of Virgil Stamps. She said her mother had assured her that Virgil composed the tune.
In 1938, the great Louis Armstrong took it up and recorded it. It was not until then that it caught on and its fame was assured.
The tune has been adopted as a rallying song for sports teams and institutions throughout the world. In my country, it is used by Southampton Football Club (The Saints). Most famously, the tune was taken to its heart by New Orleans and is the probable reason why The New Orleans Saints Football Team was so named.
Its simple chord structure is copied in other tunes. I think you will find I'll Be Glad When You're Dead, Peruna, Reefer Man, The Sloop John B, You Rascal You and Red River Valley are pretty much identical; and the tune We Shall Walk Through The Streets Of The City (played these days by most traditional jazz bands) certainly is. The Chorus of Livin' High uses this structure, too. And so do The Coming Tide and the Chorus of Who Threw the Whisky in the Well.
And a final observation: when I was in New Orleans as a tourist a few years ago, I came across a couple of jazz buskers (trumpet and banjo) in Jackson Square and they were playing When The Saints in the unusual key of E! The trumpeter was producing some amazing improvisations. As he was using a Bb trumpet, it meant he was improvising at high speed in what was for him a key of 6 sharps! It was a brilliant improvisation. I suppose these two gentlemen were playing the tune because they knew it was a crowd-pleaser; but at the same time they were choosing to make it a much greater challenge for themselves.