Based on the instrument invented by Leon Theremin Thereminvox lets you create that classic eerie sci-fi sound. Like the original instrument, there are two continuously variable controls; volume and tone. Volume is controlled by moving your left finger up and down while tone is controlled by moving your right finger(s) left and right. The tone can be raised or lower by either moving your right finger up or down or by opening your two right fingers to simulate opening and closing your hand, depending on which mode of play is selected.
Theremins are often played with vibrato so Thereminvox has an auto vibrato feature. You select the the rate and extent of the vibrato and Thereminvox takes care of the rest.
The range of tones can be selected by the user, and is limited only by the sounds your iPhone is capable of producing. Unlike the original instrument which is notorious for a lack of feedback other than the actual sound produced, Thereminvox gives you both a frequency display as well as a tuner displaying the nearest note and graphical display showing if you are flat or sharp.
The user can also select the key to play in. The key selected has no effect on the sound produced, the Thereminvox can produce a tone across its entire frequency range. The selected key only affects the grid overlay and the tuner.