  In order to expand the applicability of muon spin rotation, relaxation, and
resonance ($\mu$SR) experiments with pulsed muons and to make effective use of
the high-flux beam, we have developed a new experimental method ``transient
$\mu$SR''. In this method, $\mu$SR data for each muon pulse are tagged with
external parameters such as temperature and magnetic field in real time,
allowing the sample environment to be changed without interrupting data
collection. As a result, continuous $\mu$SR measurements under sample
conditions that vary on a time scale longer than the beam pulse interval (40
ms) are realized, and efficient beam utilization is achieved by eliminating the
lag time associated with moving between discrete measurement points. The
transient $\mu$SR method was applied to the study of the magnetic properties of
cupric oxide (CuO) and the observation of level-crossing resonance relaxation
in copper, and the method was successfully established by confirming that the
results reproduce those in the previous reports.
