  Algorithms for reliable real-time score following in live opera promise a lot
of useful applications such as automatic subtitles display, or real-time video
cutting in live streaming. Until now, such systems were based on the strong
assumption that an opera performance follows the structure of the score
linearly. However, this is rarely the case in practice, because of different
opera versions and directors' cutting choices. In this paper, we propose a
two-level solution to this problem. We introduce a real-time-capable,
high-resolution (HR) tracker that can handle jumps or repetitions at specific
locations provided to it. We then combine this with an additional
low-resolution (LR) tracker that can handle all sorts of mismatches that can
occur at any time, with some imprecision, and can re-direct the HR tracker if
the latter is `lost' in the score. We show that the combination of the two
improves tracking robustness in the presence of strong structural mismatches.
