Matthew Roddy


A Method of Morphing Spectral Envelopes of the Singing Voice for Use with Backing Vocals


The process proposed in this thesis is based on the empirical observation that it is often desirable for a backing vocalist to match his or her timbre to that of the lead vocalist when the two voices are singing the same phonetic material concurrently. This is epitomized by the common studio practice of multitracking the lead singer’s voice for use as backing vocal tracks. This thesis presents a novel application of voice morphing research for use with a source backing vocal and a target lead vocal in a studio context. Recent studies at IRCAM have shown that the interpolation characteristics of line spectral frequencies (LSFs) result in a perceptually smooth transitions between spectral envelopes when LSFs are used as morphing parameters. As such, the potential for the usage of morphing as a subtle effect to attain intermediary timbres between two voices is facilitated. This thesis combines the aforementioned research with a deterministic plus stochastic spectral modeling synthesis (SMS) system to create a version of the proposed process using the simulator Matlab. Several optimizations of morphing techniques are proposed for the unique usage context including an algorithm that performs crossfades of synthesized and unsynthesized audio on the basis of voicedness. The effectiveness of the process is evaluated and design aspects for a real-time version are considered within an adaptive-effect framework.

Matthew Roddy