Systems, methods, and computer program products are provided for producing audio and / or visual effects according to a correlation between reference data and estimated note data derived from an input acoustic audio waveform. Some embodiments calculate a pitch score as a function of a pitch estimate derived from the input waveform, a reference pitch, and a real-time-adjustable pitch gating window. Other embodiments calculate the pitch score as a function of pitch and timing estimates derived from the input waveform, reference pitch and note timing data, an adjustable rhythm gating window, and an adjustable pitch gating window. The audio and / or visual effects are produced according to the pitch score, and may be used to generate outputs (e.g., in real time) for affecting a live performance, an audio mix, a video gaming environment, an educational feedback environment, etc.