g++ can't find installed library - c++

Question

I'm trying to compile and example file which needs the required library libmusicxml.
I compiled the library as they said (cmake, make, make install) and it made and installed a bunch of files:
Install the project...
-- Install configuration: ""
-- Installing: /usr/local/lib/libmusicxml2.so.3.00
-- Installing: /usr/local/lib/libmusicxml2.so
-- Installing: /usr/local/include/libmusicxml/musicxmlfactory.h
-- Installing: /usr/local/include/libmusicxml/sortvisitor.h
-- Installing: /usr/local/include/libmusicxml/xmlreader.h
... etc
Now I want to compile one of their sample files so I run g+ filename.cpp and it gives me the following error:
libmusicxml.h: No such file or directory
Does this mean it's not seeing the library in /usr/local? Can I specify this somewhere? Set a path or something?
I have made sure to have the latest version of the libmusicxml library from here and did the same (cmake followed by make).
When I go to the gives samples and try to make one (with the provided make file, which work according to the developer) it doesn't want to do it:
dorien#XP:~/bin/libmusicxml-master/samples$ make
gcc -g -O3 -Wall -Wuninitialized -I../src/elements -I../src/interface -I../src/files -I../src/lib -I../src/parser -I../src/visitors -I../src/guido -I../src/operations countnotes.cpp ../libmusicxml2.a -lstdc++ -o countnotes
gcc: error: ../libmusicxml2.a: No such file or directory
Makefile:14: recipe for target 'countnotes' failed
-> I tried to locate libmusicxml2.a and that doesn't seem to exist.
When I run xml2guido (which seems to have a compiled version in the root directory of the package), I get:
xml2guido: error while loading shared libraries: libmusicxml2.so.3.00: cannot open shared object file: No such file or directory
However, there is a libmusicxml2.so.3.00 in the same directory
Maybe it's that the package is not linked correctly? Or something about the missing .a file?
I do think it was built correctly:
make
[ 73%] Built target musicxml2
[ 75%] Built target RandomMusic
[ 78%] Built target countnotes
[ 80%] Built target partsummary
[ 82%] Built target readunrolled
[ 85%] Built target xml2guido
[ 87%] Built target xml2midi
[ 90%] Built target xmlclone
[ 92%] Built target xmlfactory
[ 95%] Built target xmliter
[ 97%] Built target xmlread
[100%] Built target xmltranspose
dorien#XP:~/bin/libmusicxml-master$ sudo make install
[ 73%] Built target musicxml2
[ 75%] Built target RandomMusic
[ 78%] Built target countnotes
[ 80%] Built target partsummary
[ 82%] Built target readunrolled
[ 85%] Built target xml2guido
[ 87%] Built target xml2midi
[ 90%] Built target xmlclone
[ 92%] Built target xmlfactory
[ 95%] Built target xmliter
[ 97%] Built target xmlread
[100%] Built target xmltranspose
Install the project...
-- Install configuration: ""
-- Up-to-date: /usr/local/lib/libmusicxml2.so.3.00
-- Up-to-date: /usr/local/lib/libmusicxml2.so
-- Up-to-date: /usr/local/include/libmusicxml/musicxmlfactory.h
-- Up-to-date: /usr/local/include/libmusicxml/sortvisitor.h
-- Up-to-date: /usr/local/include/libmusicxml/xmlreader.h
-- Up-to-date: /usr/local/include/libmusicxml/xmlfile.h
-- Up-to-date: /usr/local/include/libmusicxml/libmusicxml.h
-- Up-to-date: /usr/local/include/libmusicxml/unrolled_xml_tree_browser.h
-- Up-to-date: /usr/local/include/libmusicxml/xml.h
-- Up-to-date: /usr/local/include/libmusicxml/elements.h
-- Up-to-date: /usr/local/include/libmusicxml/factory.h
-- Up-to-date: /usr/local/include/libmusicxml/types.h
-- Up-to-date: /usr/local/include/libmusicxml/typedefs.h
-- Up-to-date: /usr/local/include/libmusicxml/xml_tree_browser.h
-- Up-to-date: /usr/local/include/libmusicxml/versions.h
-- Up-to-date: /usr/local/include/libmusicxml/exports.h

Answer 1

Does this mean it's not seeing the library in /usr/local?
It means that it didn't find the header libmusicxml.h. You didn't tell the compiler to look for it in /usr/local/include/libmusicxml.
Can I specify this somewhere? Set a path or something?
See the documentation of your compiler. In gcc, the option for include search paths is -I.
Instead of searching for the header libmusicxml.h from /usr/local/include/libmusicxml/, I would recommend including libmusicxml/libmusicxml.h and searching from /usr/local/include. That would be simpler since g++ searches from /usr/local/include by default, so no compiler options would be required.

Answer 2

The library (and headers) weren't recognised until I ran:
export LD_LIBRARY_PATH=/addressto/libmusicxml-master
That fixed it.