Real-time implementation of vibrato transfer as an audio effect

An algorithm for deriving delay functions based on real examples of vibrato was recently introduced and can be used to perform a vibrato transfer, in which the vibrato pattern of a target signal is imparted onto an incoming sound using a delay line. The algorithm contains methods that computationally restrict a real-time implementation. Here, a real-time approximation is presented that incorporates an efficient fundamental frequency estimation algorithm and time-domain polyphase IIR filters that approximate an analytic signal. The vibrato transfer algorithm is further supplemented with a proposed method to transfer the amplitude modulation of the target sound, moving this method beyond the capabilities of typical delay-based vibrato effects. Modifications to the original algorithm for real-time use are detailed here and available as source code for an implementation as a VST plugin. This algorithm has applications as an audio effect in sound design, sound morphing, and real-time vibrato control of synthesized sounds.