Fig 1.
With so many players choosing instruments with an F valve it is easy to try and solve all ‘shift’ problems by virtually disregarding 6th and 7th position. However, in my experience clarity is frequently enhanced by the extra effort and in any case the added co-ordination required to press the valve down at the right moment in a fast passage can often be compromised when under pressure in a performance. For this reason I would recommend that the low C near the beginning of the rising scale passage in bar 21 is taken in 6th position. Be careful also to resist the tendency to get louder before actually marked in bar 27. As the human ear favours the higher frequencies, be subtle, don’t get too loud too soon and take advantage of this fact in conserving air for the rest of the phrase