AVTK is a small lightweight user interface toolkit designed for building custom graphical user interfaces interfaces. It was conceived particularly to build LV2 plugin GUIs, but is also usable for large and complex standalone programs. Focusing on user experience, AVTK promotes ease of use for novices yet affords power-users the most efficient interactivity as possible. The author feels this is particularly important in live-performance software, where user-experience and creativity are in close proximity.