As an organist, I have been working in club land in the North of England for the past 30 years or so and one of the crucial qualifications in this environment is the ability to sight read music on demand.
When I say music this can be anything from a beer matt to a ripped piece of paper repaired with selotape and stained with beer.
To be fair most of the music is written by professionals and is nice to read but not always easy.
As a club organist, you do not get a band call. In fact, you are lucky to get five minutes to scan through between 10 and 15 pieces of music. Some written in different keys, and every organist will tell you they hate it when they get the dreaded 6 sharps or 6 flats or even 7 sharp keys in a piece of music that just happens to contain a solo especially written for you.
So how do you improve your sight-reading? Well I asked my music teacher this very question as I embarked on my club land career. His answer was to practice sight-reading. He went on to tell me that session musicians practice by picking up any music book start playing on page one and continue until they have finished the book.
Does it work? Yes it does. Try it for yourself, pick up any piece of music you can find, preferably one that you are not that familiar with, then start to play, but do not stop. If you make a mistake it does not matter, you are not practising how to play this piece of music you are practising sight-reading this piece of music.
If you really want to test yourself. Get yourself an audience. I practice my sight-reading every week in front of a 200 plus audience. Its surprising how your concentration improves.