The most immediate difference between reeds is their stiffness. The softest reeds are used mainly by beginners and on mouthpieces with narrow tip openings. To use a hard reed, which you’ll find especially on mouthpieces with large tip openings you need to be able to play well. You can find out how hard or soft a reed is by its number.
Most manufacturers rate their reeds on a scale of 1 – 5, often in half steps. The higher the number, the stiffer or harder the reed.
A harder reed gives a heavier, darker, thicker or fuller sound, and makes playing softly and low more difficult.
A soft reed speaks more easily and gives a brighter, lighter sound, and makes playing softly easier.
A higher number simply means that the reed is harder, being cut from a less flexible piece of cane. It will be exactly the same thickness as a reed with a lower number, assuming it’s the same type of reed.
A reed consists of countless hollow miniature tubes or fibres with a soft material called pith between them. The pith becomes gradually softer from exposure to your saliva, until it gets soft that the reeds stops working altogether. How long that takes depends on the type of saliva you have, how often you play and on the reed itself. Reeds often last between 2 and 4 weeks
What 1 manufacturer calls a 2 may be equivalent to a 1 ½ or a 2 ½ from another brand.
Break them in
Reeds which perform very well straight away often don’t last very long. The best reeds are usually the ones which seem a little hard to begin with – in other words, they don’t initially play well.
Looking and Playing
If you hold a reed up against the light, you should see an inverted ‘V’. This should be in the centre of the reed, otherwise they are more liable to squeak and don’t blow comfortably. A good reed is yellow to golden brown in colour. A reed with an even grain is more likely to vibrate correctly than one with spots or knots. Always wet a reed before you play. Dry reeds do not vibrate well.
Information taken from “The Rough Guide to the Clarinet” by Hugo Pinksterboer.