No, not blankets or sheets.
Covers of songs are versions (variants, if you will) of existing songs.
Often times "covers" are a musician's attempt to ride the coat tails of popularity created by another music.
Currently it is not uncommon go to a concert and hear "covers" of other artists' songs.
Normally, if I wished to hear the music of another artist I would go to that artist's concert.
To me there are two types of covers:
1) One that sets out to imitate exactly the original song. Tribute bands today tend to fall into this category.
2) One that while using the same song/music by another artist the new performer tries to make it their own.
I'd never really thought about it, but choral arrangements of pop tunes are in reality "covers."
(By pop this includes film and Broadway tunes, not just popular songs.)
Choral arrangements have been written for years. They are not new phenomena.
My experience has been that most choral arrangements of popular tunes tend to be lacking in substance.
To put it bluntly, a poor substitute of the original.
There is usually a reason why a particular song was made famous by a solo artist rather than a choral group.
I recall singing a few choral arrangements of songs when I was in high school and not really liking them.
One of the challenges I face as a choir director was trying to convince my choral students about choral arrangements they might be singing.
It kind of becomes a love/hate relationship.
Normally the students LOVE a song and want to sing it.
Then when first introduced to the choral arrangement they determine they HATE it because "it doesn't sound like the original."
This dislike is often obvious in the performance.
Having said this, it is rare that a choral arrangement of a piece of music lives up to the beloved original.
I find that I am drawn to the choral arrangements that make use of a song's tune while expanding upon the harmonies. This expanding upon the harmonies allows the arranger to make it his own.
Choral ensembles are able to build sonorities that a pop group rarely can.
Currently I am preparing for a spring concert that is made up of choral arrangements of known tunes.
While some of the arrangement, "covers," are bearable and/or are growing on me, others appear to be better off unsung.
[This is not a reflection of the choral director's song selection, merely a statement that arrangements, or "covers," of songs are rarely satisfying in great number or in the long run.]