Designing Audio Effect Plugins in C++, 2nd Edition

Chapter 15Modulated Delay Effects

Perhaps the most interesting kinds of audio effects, from both listening and engineering standpoints, are the modulated delay effects. They include the chorus, flanger, and vibrato; additionally, modulated delays are also found in some reverb algorithms. These time-varying filters are actually quite sophisticated and fun to implement. We already have C++ objects designed for audio delays with circular buffers, and LFOs. These are key ingredients for modulated delay effects. Figure 15.1a shows the standard delay line with feedback. The delay is constant until the user changes it to another fixed value. In the modulated delay line in Figure 15.1b the amount of delay is constantly changing over time. The system ...