Probably the first time I've noticed that word on the Forum. Can't remember if I ever heard the Talking Heads' album SPEAKING IN TONGUES, but this seems a good place to mention it.
Guy Kyser of Thin White Rope uses a gutteral roar as a singing style and obscure poetic lyricism. I did try to slowly go through some recordings and note down what I heard. I later saw the actual lyrics written down. nothing like. Not sure if he's much better on the covers he did.
The Cocteau Twins are one of my favourite bands even tho' i rarely understand the lyrics. Brian Johnson of AC/DC is difficult for me to understand. Thom Yorke! To me he is a lazy singer, especially live, seem uninterested at times, imo, to even attempt to enunciate his words when singing.
Because, as previously mentioned, in most of Liz Fraser's lyrics in this stage of her career, she's not singing actual English words. And even when she is, they're rarely in any kind of recognizable syntax. There are some early and some late Cocteau Twins songs with recognizable lyrics -- the chorus of my favorite song from their first album is the perfectly intelligible "the devil might steady, we wax and wane" (Although I'm amused to see that not all the lyrics sites agree on that) -- but for most of their career, her lyrics are about sound instead of meaning. We can't understand her lyrics because there's literally nothing there to understand.
For Australians, James Reyne from Australian Crawl would have to be on this list. He’s been parodied a few times over the years.
Richard Jobson. I dearly love the Skids and think his voice is great, but I doubt I've ever understood a sung lyric. Maxell came to a similar conclusion in one of their 80s adverts
I’ll chime with @Danby Delight and simply add that this is also the case with most Dream Pop and Shoegazing Bands of the early 90’s. I felt even back then that the lyrics were not essential - it was the human voice’s contribution to the overall band sound - using the voice as an additional instrument - that mattered most. I think of Chapterhouse and their track “Pearl”. I love Rachel Goswell’s vocalizing on that tune. Always will. Kind of had a crush on her back then because her voice was (and possibly still is) so beautiful. If there is a heaven and I get to go there, I’ve always daydreamed about the Slowdive song “Shine” as being what heaven sounds like. Then Bach’s B Minor Mass after that.. But wouldn’t it be really enlightening to find out that Rachel Goswell (on her early Slowdive EP’s especially) and Miki Berenyi (on her early Lush-era albums) were not exactly thrilled about how those records were mixed - assuming that were true? I ask this because Jagger has gone on record multiple times about his not being all that happy with Exile’s muddiness. I agree with everyone here. I wouldn’t change anything about that album. Everything great about the Stones at their peak is there.
Hmm....might be off base some but I'd go with Magma since they sing in a language similar to Klingon.
A number of people brought up Elton. As my equipment improved over the past 45 years - from a handheld transistor AM radio in my boyhood to my current set up - the more intelligible most but not all of Bernie’s lyrics became for me on the 1969 to 1975 albums.
A few I always think about... Mick on “Exile” Jim James - My Morning Jacket on “It Still Moves” Thom from Radiohead James from Manic Street Preachers (for example... the song “Yes” on the “Holy Bible” record, quite shocking lyrics but it took me like 5 times to even make out the words!) Early T. Rex stuff
Kenny Loggins. Sings like he just bike crashed into a jungle gym with his mouth. "Maa-maw-rye. (maw-rye!) Nopaday-urrie-baw-mee. Wahya-padda-gammie-a-faah? Canya-fett-mee-fee"
Stevie Nicks, all her hits, digitally remumbled for CD. http://www.internettreehouse.co.uk/audio/snicks.mp3