In regards to pitch I agree. However there are techniques (like yodelling) to reach different harmonics to extend the pitch range of the voice.theemporer said:The human voice is limited in that it has a far lower range of pitches that it can produce than instruments such as the guitar or piano. Additionally, it lacks the ability to be played/sung at the speeds of many other instruments. It has the unique ability, however, to deliver lyrical quality at the same time as melodic quality, something no instrument can do. Also, it offers more easily understood emotional depth than any other instrument.
I wouldn't call it the "most versatile" instrument but definitely a unique and important one. I think, for a piece meant to mean something specific that is not not designed for accompaniment that would explain it (video game music, plays, etc. ), lyrical music does work best. If a piece is merely meant to exhibit more general emotion or accompany another work, an instrumental piece works better as lyrics would distract from the emotion or whatever is happening in the accompanying work.
Also in regards to most versatile, I think only a synthesizer can produce more sounds and textures than the voice can.
In regards to expressing emotion... I don't think it matters too much. I consider the voice as an instrument itself rather than something seperate. You can convey emotions through speech, IMO it's the strongest instrument in regards to expressing emotions, because they are, for lack of a better word, more real. It's a real person conveying these feelings, rather than through an instrument.
This sounds kinda stupid but I am just thinking... why does adagio for strings sound sad? Why does the phrygian dominant scale sound "egyptian"? Why do bells make us think of christmas?