The clarinet is a member of the woodwind family—but sometimes we forget to think about the “wind” part of “woodwind”. Our “wind”, the breath we put into the instrument, is what causes it to make sound. How do we develop good air support?
Air must move through the clarinet (technically, across the reed so it vibrates) to make sound. It doesn’t take a lot of work to make sound—but it takes a bit more effort with air support to make rich, full clarinet sound. We do this by using our lungs and supporting muscles in a specific, intent way.
Normal breathing doesn’t utilize all our lung capacity; we use more of it when exerting ourselves in some fashion. Playing a wind instrument is one of the situations in which we want to use more of our lung capacity, so we have the air support we need. To practice getting good breaths, sit upright in a chair with your feet flat on the floor (you may not be able to be against the back of the chair), making sure that your body from the hips up is erect, but not stiff (“standing from the waist up”). Think of your lungs as balloons that you must fill up, all the way down to your belly button, and breathe in deeply keeping the body relaxed as you do so. Your torso will expand outward in all directions—up and down, but especially out to the front and back, so that your lungs have the room to fill up. Check that your keep your shoulder, neck, and throat muscles relaxed as you breathe in. Hold this breath in for a moment, and then release it. Try it again several more times so it feels more comfortable.
Breathing in is important, but so is breathing out—after all, we must get the air through the clarinet at some point! When breathing out, we want to fill the clarinet with as much air as possible, but also be able to control that stream of air so that we don’t use it all up at once. When you take a solid breath in, just as you are about to breathe out, engage your core muscles (stomach muscles, back muscles, etc.—the torso area), a bit like holding a sit-up or crunch, so those muscles are in use as you blow the air into your clarinet. See how long you can sustain one note with this technique. Is it longer or shorter than you could do before? This kind of breath support helps us create a rich, full, mature clarinet sound, too. Do you notice a change in your sound quality? Practice this technique several times on one or a few notes with the solid breaths in that are described above. Then try it while practicing scales, arpeggios, etudes, etc., to get into the habit of supporting your clarinet sound with deep, solid breaths in and core-supported breaths out.
You may find yourself getting physically tired as you practice—you’re asking your body to do a task in a new way, using different muscles, so this fatigue is normal. Try to practice good breath support every time you pick up the instrument, every time you take a new breath, every time you re-start a passage in a practice session, and so on, until it becomes second nature. And there are a couple of ways to check for the engaged-core-muscle feeling: if you have access to a yoga ball, try playing clarinet while sitting on it. Your core muscles are what will keep you still enough to play, so they will be working! You can also sit on a chair and stick both legs straight out, lifted from the floor. Holding them in place while you play clarinet will also require engaging your core muscles.
These are a couple of tips that you would need to be able to develop the air support that you would need to play the clarinet. You can also find additional great sources with a different, but effective approach to air support here.