While music & music history are often studied to some degree as part of music & history courses, it is beneficial to have a single course dedicated entirely to music history.
When music history is taken as its own course, it makes it easier to see how it evolved through the ages.
Norton’s Anthology of Western Music is often used by universities as the source for their music history courses.
While most courses are several volumes, this edition covers music history in one volume.
Free powerpoints of lessons can often be found online.