List of artists that have never lost quality throughout entire career


One of the brightest on my list is 

1. Depeche Mode. I'm big fan started listening and enjoying them from their very first album "Speak and Spell". I am devoted to their perfection of every song they create in terms of sound, melody, harmony and incredible intelligence. Their music may seem simple, but in reality much more complex than seems. I believe that they're somewhat commercialized, but also believe that they deserve their incredible success. They're indeed Kings of electronic rock!

2. Can (The Can). Every album they released is a journey to their creativity. What are they rock? Jazz? Prog? Their music often can cover all styles of music in one song. It's a blend of jazz-trained drummer Jaki Libezeit, classically trained keyboardist Irmin Schmidt(also conductor and neo-classical composer and film score composer), multi-instrumentalist bassist Holger Czukai and classically trained guitarist and electric violinist Michael Caroli (RIP). It's a unique blend of musicians with extraordinary skills and creativity

3. Dead Can Dance. This artist has plenty of praises and each and every of their album is a unique blend of electronics and earth bound instruments. Lisa Gerrard is known to be a part of Gladiator Motion Picture Soundtrack.

4. Tom Waits. Many would criticize Tom for not singing his own voice, but I'm amused the way he does it with spirit of Louis Armstrong! Yes indeed with spirit instead of just imitating. Embracing the spirit of inspired artist is different and Tom is clear example to that!
czarivey
It's true with many classical performance ways to define moods and change pace towards benefit of a certain instrument or a sound, but that's not defined as improvisation.
Classical players pay attention to other players and good ones adjust to same . That's improv to me .
@dragunski 
Most of Brandenburg Concerti played mediocre or boring perhaps except Richter piano transcription.
Top of the heap ... Sarah Vaughan. She never lost it. Not one iota. In fact, her instrument continued to grow right to the end. Perfect pitch and a voice that emulated a wonderfully lush tenor saxophone that tenor saxophone players only wished they could duplicate.

Try the last two cuts of this album, "A Foggy Day in London Town" and I’ve Got a Crush on You" to see what I’m talking about:

http://www.ebay.com/itm/Gershwin-Live-by-Michael-Tilson-Thomas-Sarah-Vaughan-CD-CBS-Masterworks-/391...
I hear you oregonpapa. Here's another Gershwin studio recording with Hal Mooney, a young Sarah and also a cd of the rehearsal cuts to give some insight into how talented and gifted that lady really was, just incomparable. Her voice got a bit smokier and richer as she aged but her interpretative skills just kept growing.

https://www.amazon.com/Sarah-Vaughan-Sings-George-Gershwin/dp/B00000AFEZ/ref=ntt_mus_ep_dpi_1