xoxos is a music software project by Rurik Leffanta, based in Tucson, Arizona. The project is focused on VST instruments and effects for Windows, with a catalog of more than fifty plugins spanning physical modeling synthesis, algorithmic sound design, and procedural audio. Leffanta's work leans toward unconventional synthesis approaches, including waveguide and friction-based string models, formant-based voice synthesis, and chaos/feedback oscillators.

Notable releases include the Sounds of Nature collection, which emulates wind, rain, thunder, songbirds, and insects and won first place in the KVR Developer Challenge 2007. Other widely discussed plugins include Fauna, a waveguide vocal tract model for abstract and animal voices; Syng3, a seven-formant voice synthesizer; Angle, a 3D oscillator paired with filtered feedback for atonal textures; and physical models such as Boing2 (bowed string) and Piamo (virtual piano).

The xoxos catalog was made freeware in 2009, and the plugins have since circulated as a reference point in the VST sound-design and physical-modeling community. Leffanta's work has been covered in Sound on Sound and other music production publications, and is often cited on KVR Audio and rekkerd.org for its experimental approach to synthesis.

xoxos has 3 products cataloged on Equipboard, including Virtual Instrument. Their gear is featured by 1 artist, with the strongest followings in Electronic, Rock, and Hip Hop. Notable users include emma essex.