A well known recording trick is to pitch a song in a key that is slightly too high for the singer, so the straining for notes performance. Motown writers like Holland-Dozier-Holland used to pitch songs in keys that were just a bit too high for M Stubbs of The Four Tops, to bring out more passion in their voices. But if you’re going to sing your songs live, don’t use many  or you’ll never get through a set with your voice intact. The opposite effect is not so common, but worth conside something from Michael Stipe singing at the low end of his range, and as for Lee Marvin’s ‘Wanderin’ Star’. . . .With age, the voice naturally loses some of its range. This has had an interesting consequence for a singer-songwriter like relied on altered guitar tunings. Over the years her tunings have had to move down to match the drop in her voice  problems as the guitar strings have got slacker.