A user interface, a method, and a computer program product are provided for enabling a user to voice control over at least one setting of an apparatus such as a lighting system. The user interface determines a characteristic of an audio signal converted from vocal input of a user. A first setting of the apparatus is adjusted proportionally to a variation in the characteristic. Another setting of the apparatus may be adjusted on the basis of another characteristic of the audio signal. As a result, the user interface enables the user to control a lighting system over a substantially large or continuous range of output.