International Symposium on Music Information Retrieval:.

Abstract:
This paper presents a new toolkit for the creation of customized structured document recognition applications by domain experts. This open-source system, called Gamera, allows a user, with particular knowledge of the documents to be recognized, to combine image processing and recognition tools in an easy to use, interactive, graphical scripting environment. Additionally, the system can be extended through a C++ module system.

URL
http://dkc.jhu.edu/gamera/papers/ismir2001b.ps