In music, a score is a written out version of the music. It's the document a conductor has, with all the parts on it. Score reading is when you listen to the music while following it written down. It has been used by generations of music students to help them in lots of ways. Seeing the music helps you to hear more, and hearing the music helps develop your music literacy.
If you sing or play from sheet music you are having to deal with making the sounds as well as reading the music. When you are score reading you don't have to produce the music – just practise matching your ear and your eye in real time. It's a bit like when you were a child, looking at the book while someone read the words to you.
Score reading is included in these materials for three main reasons:
To help the many adults who sing or play in groups and say they don't find it easy to hear what is going on in the other parts
To help people seeking to improve their music reading
To enrich the experience of listening to music, live or recorded
Twenty years ago, getting into score reading would have involved buying or borrowing recordings. Nowadays we've got online performances – thousands of them. YouTube is a brilliant resource. There are usually several performances to choose from, it's easy to stop and start and repeat and there's a timer to help you find particular places.
Furthermore, lots of the videos have a score, that moves along with the music. Some of these scores are graphic, others are in music notation. Both are useful helping you to notice more. The early activities, using short pieces, offer you a score to print out. As you progress, you'll be invited to visit on line sites such as the Petrucci Music Library, which has thousands of non-copyright scores that you can download. Public Libraries keep some scores. You might sometimes want to print out a score. When it's on paper you can use your finger to follow – it's not always easy to keep your place, and you can write on it.
The starting point is being able to follow a simple piece of piano music, tracking the notation at the speed of the music, and matching what you see you what you hear. As you progress, you'll be able to cope with more lines, and more complex music.