San Francisco composer Pamela Z weaves elaborate arrangements from looped, processed, and sampled vocals, combining elements of operatic singing, poetry, and speech in her dazzlingly virtuosic, avant-garde performances. In recent years, she has developed a unique process that relies on an ultrasound-powered MIDI controller that allows her to process her singing and trigger samples in real time solely using hand gestures, as opposed to twisting knobs and pushing buttons. Simply put, her live shows are a sight to behold. At Yerba Buena Center for the Arts in San Francisco on April 28, Z will perform one of her most ambitious works yet: Memory Trace. For the piece, the musician interviewed dozens of subjects about their experiences with memory and perception. The resulting interviews became fodder for Z to sample, and the piece incorporates live singing, monologue, and a video installation to probe the malleability of the human mind.