Very-Long-Period (VLP) volcano seismicity often represents subsurface magma resonance, and thus provides insight into magma system geometry and magma properties. We develop a signal processing workflow using wavelet transforms to detect and assess period, decay rate, and ground displacement patterns of a wide variety of VLP signals. We then generate and analyze a catalog of VLP seismicity over the 2008-2018 open vent eruptive episode at Kilauea Volcano, Hawaii USA. This eruption involved a persistent lava-lake, multiple intrusions and rift zone eruptions, and a climactic caldera collapse, with VLP seismicity throughout. We characterize trends in two dominant magma resonances: the fundamental mode of the shallow magma system is a vertical oscillation of the magma column in the conduit/lava-lake, and higher frequency modes largely consist of lateral lava-lake sloshing. VLP seismicity was mainly triggered by lava-lake surface perturbations, and less commonly from depth. Variation in event period and decay rate occurred on timescales from hours-years. On timescales of months or less these changes were often correlated with other datasets, such as ground tilt, SO2 emissions, and lava-lake elevation. Variation in resonant properties also occurs over days-months preceding and/or following observed intrusions and eruptions. Both gradual and abrupt changes in ground displacement patterns indicate evolution of shallow magma system geometry, which contributes to the variation in resonant modes. Much of the variation on timescales of months or less likely reflects changing magma density and viscosity, and thus could inform a variable shallow magmatic outgassing and convective regime over the ten year eruptive episode.