1965 and before. Early Paul. He was still exploring his range and did not have as much control or move as easily between styles within the same song.(quora.com)
1966–mid 68. Emerging Paul. Better control, some powerful performances. Pushing his voice to new limits.
late 68 - 75. Peak Paul. All of his power and range are there. Maybe I'm Amazed is a highlight but numerous other examples from Oh Darlin to Call Me Back Again. Even trifles like the cover of Love Is Strange on Wild Life are amazing performances. The world tour tested his voice and brought it back to reality.
You can hear that inexorable process play itself out in singers who keep at it long past their prime. In his youth, Paul McCartney produced a wondrously pure schoolboy tenor, with a touch of sandpapery sexiness. At 74, he can still usually hit the high note on “night” in the opening line of “Blackbird,” but the lightness has
been scrubbed away, replaced by an uncertain warble. There is almost always a trade-off between agility and age. Singers don’t want to retire, and fans don’t want to lose them, but the price of longevity can be steep. (Vulture)
Paul Simon has kept his voice in remarkably good shape, but when he found himself in vocal distress singing “Bridge Over Troubled Water” at the Democratic National Convention in July — a song Art Garfunkel originally sang, in his higher range, though Simon’s been performing it for years — Twitter reacted with a hailstorm of condescension and scorn.
81–89. Eighties Paul. For whatever reason didn't test his voice on rock as much. Some great ballad performances like Through Our Love. The 89 tour brought it down another notch.
Threatle Paul. The voice heard in Free As a Bitd. Still better than most pop singers but losses in the upper ranges. Flaming Paul. The voice heard on the later recorded Flaming Pie tracks and through Chaos and Creation. In hindsight still capable of astounding (This Never Happened Before, Somedays).
06–13. Declining New. A pretty evident decline even betweenDance Tonight in
Throughout their careers, McCartney, Simon, and Bennett have shared a couple of stylistic advantages: They confined themselves within a relatively narrow range, and they let the microphone supplement intimacy with volume. The same cannot be said of Steven Tyler, the 68-year-old Aerosmith front man who has required surgery to keep his voice in shape.
