  We study indeterminacies in realization of ornaments and how they can be
incorporated in a stochastic performance model applicable for music information
processing such as score-performance matching. We point out the importance of
temporal information, and propose a hidden Markov model which describes it
explicitly and represents ornaments with several state types. Following a
review of the indeterminacies, they are carefully incorporated into the model
through its topology and parameters, and the state construction for quite
general polyphonic scores is explained in detail. By analyzing piano
performance data, we find significant overlaps in inter-onset-interval
distributions of chordal notes, ornaments, and inter-chord events, and the data
is used to determine details of the model. The model is applied for score
following and offline score-performance matching, yielding highly accurate
matching for performances with many ornaments and relatively frequent errors,
repeats, and skips.
