A machine causes a touch-sensitive screen to present a graphical user interface that depicts a slider control aligned with a word that includes a first alphabetic letter and a second alphabetic letter. A first zone of the slider control corresponds to the first alphabetic letter, and a second zone of the slider control corresponds to the second alphabetic letter. The machine detects a touch-and-drag input that begins within the first zone and enters the second zone. In response to the touch-and-drag input beginning within the first zone, the machine presents a first phoneme that corresponds to the first alphabetic letter, and the presenting of the first phoneme may include audio playback of the first phoneme. In response to the touch-and-drag input entering the second zone, the machine presents a second phoneme that corresponds to the second alphabetic letter, which may include audio playback of the second phoneme.