Liquid fragility characterizes the rate of drop off in viscosity of a glass-forming liquid as its temperature increases above the glass transition. This property is fundamental to glass physics and of critical importance for engineering applications, yet its origin is unclear. Competing theories suggest that vibrational properties may play a role in fragility by contributing entropy to the large excess entropy of the undercooled liquid over the crystal above the glass transition. In this talk, we will demonstrate the use of in situ inelastic neutron scattering to probe the vibrational properties of a series of glasses with varying fragilities. We will demonstrate that event-based neutron scattering allows collection of the phonon density of states in as little as two minutes, enabling capture of vibrational dynamics in the narrow stable window of the undercooled liquid. We will discuss the correlation between excess vibrational entropy in the undercooled liquid and liquid fragility. Finally, we will discuss these new results in the context of a universal understanding of fragility and vibrational contributions to the thermodynamics of the glass transition.