#1
It seems that for the past few weeks I've had a dramatic decrease in my vocal range and endurance

I haven't been sick,so I'm beginning to get worried
So I'm wondering if maybe my voice suddenly deepened and I've lost my range for good?
Or maybe it'll just go away and I'll get my normal voice back

I'm just not sure
And I'd hate for years worth of songs to have to be abandoned because I can't sing them
Yes.
#2
i'm guessing by the date you registered that you haven't just hit puberty, but that'd be my immediate thought. have you had a throat infection at all? get yourself down to a doctor really - medical advice ain't allowed on here.

Vocal ranges can change if you strain them, a mate of mine permanently changed his vocal range from a bass to a tenor (albeit a low tenor) by trying sing too much jamaroquai :p
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