PitchStill gives you a note, plays the sound, and listens through your phone's mic while you match it on your instrument. Hit it clean and fast - score goes up. Miss it - streak resets. Sessions run 30 seconds to 10 minutes. That's the whole loop. It sounds simple and it is. The thing being trained is the gap between hearing a note and landing it on your instrument without hesitation. That gap is real, it's measurable (the app tracks your average time to detect), and it gets smaller with reps.