  The quality of Optical Music Recognition (OMR) systems is a rather difficult
magnitude to measure. There is no lingua franca shared among OMR datasets that
allows to compare systems' performance on equal grounds, since most of them are
specialised on certain approaches. As a result, most state-of-the-art works
currently report metrics that cannot be compared directly. In this paper we
identify the need of a common music representation language and propose the
Music Tree Notation (MTN) format, thanks to which the definition of standard
metrics is possible. This format represents music as a set of primitives that
group together into higher-abstraction nodes, a compromise between the
expression of fully graph-based and sequential notation formats. We have also
developed a specific set of OMR metrics and a typeset score dataset as a proof
of concept of this idea.
