Fox Bocals
The bocal is, by far, the single most important part of the instrument. It dominates the instrument's response, resistance and tone. It affects the overall pitch of the instrument as well as the relative intonation and should be selected with the same care that one would use to acquire the instrument itself. Even a mediocre bassoon may have a reasonably good sound and scale if it is properly fitted with a good professional bocal.
The bocal length moderately affects the overall pitch of the instrument. It most strongly influences the middle and upper middle registers because the lower register is relatively fixed by the bore of the instrument, and the extreme upper register is dominated by its own flexibility. Fox long and short bore models are normally tuned with a 3 *CVX* bocal. This includes Models I, II, III, IV, 220, 222, 41 and 51 (long) and Models 101, 201, and 240 (short). Thick wall models (601 and 660) are normally tuned with a 3 *CVC*. When trying Fox bocals, it is best to start with a No. 2. Changing bocal lengths is most frequently desirable when minute adjustments are desired for the sake of comfortably blending with other instruments. Changing bocal lengths will not help much when trying to change the pitch from A-442 to A-440. This will require changing reed designs, changing bocal bores, or changing instruments.
It is generally advisable to try a professional bocal on your instrument if it has wild notes in the middle register, or if the intonation or tone is not uniform in the middle or upper registers. It is also advisable to try a Fox bocal just to hear the improvement in the sound and freedom of blowing the instrument.