Sentence:  The duet was in <WSD>alt</WSD>; one stormed, the other half crying, half scolding, made up in volubility what her aunt possessed in authority, and it was not 'till Lady Meredith had twice raised her mild voice, either party could be silenced. 
Meaning of the word marked with <WSD> tags:  High pitch, of a voice or instrument; especially, the octave above the top line of the treble stave. (from 16th c.)