Remember that 'tonguing too hard' and 'failure to completely seal the tone holes' are the most common reasons why low notes sound weak or do not sound at all. This exercise should be played at a steady speed, checking that each note sounds clear and full-toned. Pay particularly attention to the notes C, C#, D and D# which do not like strong tonguing. Use a soften tonguing stroke or try dropping the tongue inside the mouth as you start the note as a way of reducing the breath pressure and so avoid the risk of overblowing. A good player choses the tonguing stroke that is best for each particular note varying the stroke as the instrument requires. Always be sensitive to what works best on your recorder - do not make the common mistake of believing that you play the recorder - rather, it is the recorder that tells you how it wants to be played.