> recognise the shape of a scored note, minim, crotchet, quaver on a 5 x 9 dot grid

Reading music off a lined page sounds like a fun project, particularly to do it from scratch like 3Blue1Brown's number NN example[1].

Mix with something like Chuck[2] and you can write a completely clientside application with today's tech.

[1] - https://www.3blue1brown.com/lessons/neural-networks

[2] - https://chuck.stanford.edu/