The Sound Sanctuary is a multi-species plant ensemble centered around a towering money tree (Pachira aquatica) and four rubber trees (Ficus elastica). Electrodes attached to the leaves detect subtle changes in electrical conductivity caused by the movement of water during photosynthesis. This biological data is translated into MIDI, the digital language that allows electronic instruments and computers to communicate musical notes, effectively giving the plants a musical voice. While the Sound Sanctuary determines the underlying notes and tempo, a synthesizer connected to the plants allows human collaborators to shape the sound through filters and tonal adjustments. The result is a one-of-a-kind interface for interspecies musical collaboration.