Boulder, Colorado has an altitude of 5,328 feet (1,624 meters). When traveling from a lower altitude to a higher one, generally two things happen to oboe reeds:
1.The opening becomes more closed which tends to cause sharpness 2. The reed tends not to vibrate as much as it did in lower altitudes.
If you try to scrape more cane off of your sea-level reed when it is at high altitude in order to make it more vibrant, (to solve problem #2 above) it tends to weaken the cane, thus exacerbating the reed opening issue. (Increasing problem #1 above) Most people when trying simply to scrape more cane at higher altitudes find their reeds thinner sounding and buzzier than normal.
The only real solution is to use cane from a smaller diameter tube. At sea level I usually use cane from 10-10.5mm dimeter tubes but in Colorado I use 9.5-10mm. This might seem extreme but really it just makes the openings in Colorado similar to those at sea-level.
Because one must scrape more cane off of the reed to get the reed vibrating well at higher altitudes, the cane must have the inherent strength to take that extra scraping and still produce a reed with substance in the sound. Soft cane doesn’t work well at high altitudes. Strong cane tends to be more vibrant and if you have vibrant cane at the correct diameter, you have a reasonable chance of making a reed that works.
Try not to have too thick a gouge. Again, because of the reluctance of the reed to vibrate, if the gouge is too thick, it requires more scraping to get it to play. I recommend .57-.59mm in the center of the cane.
When I travel to different altitudes I prepare my reeds (on appropriately sized cane) by getting them tied and just starting to crow. I leave them a little long so I have room to finish and clip them at my performance altitude. If they are starting to crow before I leave, I can usually begin to practice on them after one more scraping session at the destination. It is best to have a few days to finish and break-in your reeds before you need to play in public.
If you absolutely have no time to make a new reed at your higher altitude, look for a reed at sea level that is flat and rattles. Since a good high-altitude reed becomes flat and rattles when you bring it down to sea-level, it stands to reason that it might work the other way. No guarantee, of course, but at least you stand a fighting chance. Be prepared to adjust the reed when you reach your destination. Always travel with your knife, plaques, cutting block, razor blade (or whatever you use to clip reeds) and sharpening equipment. Don’t forget to pack these in your checked baggage!
Peter Cooper Principal Oboist, Colorado Symphony Teaching Professor of Oboe, University of Colorado Boulder, College of Music