Glynis Johns is also my personal favorite as well. Of course, she was the original “Desiree” in
A Little Night Music and the song was written for her. She didn’t have a typical singer’s voice and had limited range but it was due to her inability to sustain notes that he wrote “Send in the Clowns” in such a way that fit her voice perfectly - He mentioned that none of the lines in that song end with vowel sound so the singer wouldn’t draw out the last word and was full of short phrases. His genius was recognizing that despite the fact that Johns wasn’t a typical singer, she was a singer nonetheless and worked with her talent to come up with material that worked with her strengths and worked with her character. If you want to see an actual non-singer sing the song watch the Elizabeth Taylor rendition in the maligned film version of the musical. We know Taylor is an amazing actress but a singer she really wasn’t despite arguably having a voice with “range” that was within Johns abilities. It shows even with a limited voice, there’s still a difference between being able to sing and not.
The reason I love Johns version is because she sings it in-character of Desiree and adds anger and spite to it when so many singers focus on the sorrow and lament a tinge too much.