Work, Quiche, Salsa, Song

I've had two additional rehearsals with the chorus at work. Last month we learned a song in French and had quiche. Today we did one in Spanish and had chips and salsa. For the Spanish song, there are two lines - what they're calling alto and soprano. The alto line carries the melody and the soprano line has harmonies and background. Alto... that's what I sang in my high school chorus, but there the sopranos always carried the melodies and the altos did the harmonies. Well I sang alto except for the Hallelujah chorus, when I sang tenor since there weren't enough boys in chorus. Isn't that nuts? I sang tenor? And now I'm a soprano! I can't even fathom singing that low now. So what is alto? Mezzo-soprano? Lower than that?