Seems like when people with British accents sing, the accent disappears. Even if they have a really emphatic Cockney or posh or Liverpudlian accent, still, the act of singing seems to smooth it out. Why do you suppose this is?
Speech and singing are handled by different parts of the brain–it’s why speech therapists have stutterers sing their words on one note, because a lot of people with speech impediments don’t have them when they sing. It’s why I don’t trust country singers who don’t have much of a southern accent when they speak but it’s all of a sudden Twang City when they sing–it has to be done deliberately and it’s fake AF.
Singers are deliberately taught to lengthen their vowels, because you can’t sing a note that goes on for a bar and a half on an “æ”, “e” or “I” vowel, but it’s just fine on an “e:” or “i:” (to go all IPA on you…)
It just happens, that American accents seem to be quite heavy on the long vowels, compared to UK (or Australia/NZ in fact). So from your POV that sounds like “their accent disappears”. From mine, “they sound American”.
My singing teacher would re-write lines for me with the vowel sounds he wanted, so that, eg
“And I think to myself, what a wonderful world” would become
“Air-nd Ah th-air-nk too m-ah-s-air-lf wh-ah-t ah w-ah-n-d-ah-fool w-ah-ld” to remind me to do it. (The interpolated "r"s disappear in a non-rhotic accent … the scheme worked well enough for me)
There are a few vocalists who seem to express their accents, famously the brothers Reid aka The Proclaimers are very Scottish -
Lindisfarne would often allow their North East accents to dominate
Elbow - with lead singer Guy Garvey is well known for retaining his strong local accent
Sean Ryder - he guested on Gorrillaz song which was originally meant to be called 'There' but his strong accent resulted in a change and its now called 'Dare'Kaiser Chiefs - a toned down Yorkshire (Leeds) accent but its still there
Arctic Monkeys - cannot mistake that Yorkshire(Sheffield) accent
There was something of a trend amongst the UK indy world to emphasise their local accents from the late 1980s onwards, but using a strong regional accent is nothing new - Gracie Fields You could go on to mention George Formby, and definitely the old music hall starsGeorge Formby senior
one theory for rock and roll singers is they are trying to sound American like Elvis, Chuck Berry , etc. because USA is where rock got started.
This topic seems to come up at least once a year.
My standard go to response is to refer to The Pipettes. Esp. any song with “dahnce” in it.
Or the underrated Girl Ray, especially in Go Back At Ten.
I am an avid musician and musical listener, by the way, and especially interested in British music, so I would be happy to discuss it with you anytime. I am always seeking people to talk to about music.
You never heard I’m 'Enery the Eighth, I Am or Mrs. Brown You’ve Got a Loverly Daughter by Herman’s Hermits. 
I believe the singer deliberately emphasized his accent, but it shows that it’s certainly possible.
I’m guessing mentioned in threads past: for bands that do retain their Brit accents - a lot of oi/punk bands do that, like Cocksparrer, Angelic Upstarts, Cockney Rejects, among tons others.
And then there’s yankee bands that adopt Brit accents, like The Dropkick Murphys. When I was kid I always thought Styx and Rush sometimes let in the eensy slightest hints of a Brit accent.
Could never figure out if Irishman Shane MacGowan’s vocals were more Irish or British sounding.
Well he was born in England and spent most of his life there, a prep-school boy and Westminster School scholarship boy so I’d imagine his accent could be whatever he wants it to be.
Listen to the Kinks. They are from working class Muswell Hills, in the London area I think. I’m a septic, so have no clue.
Ray Davies can be unintelligible when he speaks. Listen to early interviews and some of the live album banter…
Seppo.
Interesting answers, all! Thanks for replying.
On Ministry’s first album, the very American Al Jourgensen sings in a fake British accent: Ministry - Revenge HD - YouTube
Johnny Rotten of the Sex Pistols had that London accent.
Maybe Punk doesn’t qualify as singing. Although IIRC, the Scottish Punk band the Exploited din’t sound Scottish.
As Jimmy Rabbit said to the Commitmentettes " Don’t use yer own accents. It’s ‘Ride Sally Ride’ not ‘Roid Solly Roid’."
Mick Jagger and John Lennon did, Peter Noone didn’t. Messrs. Jagger and Lennon practiced American elocution. Mr. Noone did not.
Adam Ant turned his Cockney accent on and off as it suited him. It was especially strong in Stand and Deliver.
What? I’m having an Adam Ant phase.
A good example is Keith Urban. When I found out he’s a kiwi I was surprised, to say the least.
I was all set to post that you must have confused Keith Urban with Karl Urban, but damned if they’re not both from New Zealand.