1st Q: What common characteristics can you find in the works of composers like Holst, Vaughan Williams, or Grainger? I list these three in particular because of their propensity to build on existing folk songs
A: Well, the early 20th century was a period of English folk song revival. Many composers wrote in the genre of the time. It's more accurate to say ...
As requested collating into answer-form.
Could fill out more interesting details of singer/composer in some cases if desired
Sunta hai Guru Gyani
I think most religions have "ritual" music and in modern times this probably has evolved into something like gospel or what you are referring to.
Some examples are:
Jewish cantorial music. This can be very inspirational, very emotional. In modern synagogues such music will be played with a modern "folk music" style twist. There are also modern ...