  The collective mode spectrum of a symmetry-breaking state, such as a
superconductor, provides crucial insight into the nature of the order
parameter. In this context, we present a microscopic weak-coupling theory for
the collective modes of a generic multi-component time-reversal symmetry
breaking superconductor, and show that fluctuations in the relative amplitude
and phase of the two order parameter components are well-defined underdamped
collective modes, even in the presence of nodal quasiparticles. We then
demonstrate that these "generalized clapping modes" can be detected using a
number of experimental techniques including ac electronic compressibility
measurements, ultrafast THz spectroscopy, and microwave power absorption.
Finally, we discuss the implications of our work as a new form of "collective
mode spectroscopy" that drastically expands the number of experimental probes
capable of detecting time-reversal symmetry breaking in unconventional
superconductors such as Sr$_2$RuO$_4$, UTe$_2$, and moir\'e heterostructures.
