PlayScore 2 can find and play short pieces of music in a page of text as well as whole pages of music. The music has to be reasonably clear, but PlayScore can find them itself; you don’t need to mask out the text in any way. To give PlayScore a good view of a particular music example you can snap that area rather than the whole page. But photograph the whole example, never clip the music.
NB It is not a good idea to cut out a little section of with a photo editor. This doesn’t improve the resolution and will never be better that using the whole image as it is. If you do this, PlayScore may simply interpret it as a low resolution image.