History
Since the introduction of the Triebert System 6, aka Conservatoire system oboe, in 1881, oboes have had two right-hand A-flat key options, accessible to the side of the index finger. Before this, depending on the model, it seems that there was often a key located here for either the C or B-flat or for trills for these same notes. I'm not clear on the specifics. But with the System 6, mechanisms involving B-flat and C were moved to the F# key, which left this area free for providing the alternative A-flat keys.The fingering chart in Georges Gillet's Studies for the Advanced Teaching of the Oboe (from 1938), shows two right-hand A-flat key mechanisms that are still on today's oboes. Both keys function to open the same hole as the left-hand A-flat, and are thus acoustically identical. The lower option only functions as an alternative to the normal left-hand A-flat. The higher of these two keys also contains a mechanism to facilitate the G#-A trill. It seems, though, that Gillet did not advocate for either key being used as an alternative to the left-hand A-flat. In both of the very first two etudes, where the music starts with a difficult A-flat major passage, he expressly directs the student to use the left-hand's 5th finger to hold down both the A-flat and E-flat keys in order to play the two notes in legato succession, even though this would be a natural place to use the right-hand A-flat.
Can we take as evidence for the continued avoidance of right-hand A-flat the fingering chart of Albert J. Andraud's Practical and Progressive Oboe Method (written in the 1950's)? In this chart, the fingerings are not even listed as alternatives, but only show up as trilling options. That the usage of this fingering remains rare to this day can be inferred from John Ferrillo's Orchestral Excerpts for Oboe, in his commentary to an audition excerpt from Bartok's Concerto for Orchestra, movement V (mms. 188 to 196), where he writes:
It would be good to use the left-hand F on the downbeat F's, but it is much cleaner sticking to the forked F throughout. The left-hand F requires you to use the right-hand A-flat -- a bit awkward, particularly under the pressure of an audition.
Benefits
As shown in the comment by Ferrillo above, a benefit of the right-hand A-flat is that it facilitates the use of the left-hand F, a fingering that is acoustically identical to the right-hand F, and considered superior to the forked F. While this benefit is compelling, it apparently has not been enough of a reason on its own to motivate oboists to invest the work needed to master the use of the right-hand A-flat.Another benefit arises when comparing the releasing of the A-flat keys. Releasing the left-hand fifth finger is not a slam dunk. The little finger cannot simply wait directly above the key it just left, if the next note is not A-flat. The distance from the A-flat key to the left F or left E-flat is considerable and must be traveled quickly, perhaps even as part of the release motion, if one of these other notes is to be played soon. This is not an issue with the right-hand A-flat. If we know that we are not going to use the left-hand A-flat the holding position of the fifth finger becomes less complicated, as it has a smaller area to cover.
Perhaps the biggest advantage, though, is that one can smoothly reach any note from the right-hand A-flat, and conversely, one can smoothly reach the right-hand A-flat from any note on the oboe. This is a big difference from the left-hand A-flat, where one cannot get to low B-flat, low B, left-hand F, or left-hand E-flat (barring the use of Gillet's recommended two-keys technique) without first picking up the finger and allowing an intermediate note to sound.
For classical repertoire and performance, advance preparation is the norm. The oboist can determine a fingering for pretty much any situation, working out a path through note alternatives that allows one to retain the left A-flat as much as possible, and can isolate for practice those few situations where the alternate fingering is an absolute necessity. With modal Jazz, where improvisation is stylistically restricted to a single mode or scale, the chance of finding oneself in a fingering dead-end is much less of a problem.
However, with improvising Jazz standards, with their frequent chord changes and modulations, the challenge of coming up with musical ideas in the moment is already difficult enough without having to plan for avoiding fingering cul-de-sacs! The right-hand A-flat might not be quite as facile as the left, but the benefit of being able to come and go freely to a central note on the instrument is huge. I would even venture that the limitations that arise from the inability to play passages that include the left-hand A-flat may be one of the reasons the oboe is commonly considered to be inherently unsuited for improvising Jazz standards. The use of the right-hand A-flat goes a significant way towards eliminating that concern.
Making it Work
Is the right-hand A-flat more difficult to play than the left-hand A-flat? I would have to say yes, but not by as much as some might protest. With an adjustment to the wrist and thumb, the right hand can be placed in a position where all the keys can be reached quickly and easily. With this, the right-hand A-flat can be played with a slight pressing of the middle knuckle of the index finger and/or a slight rotation of the wrist. The movement can be almost as minimal the movement of an optimally positioned left-hand fifth-finger over the left A-flat key. As testament, consider the fluidity of passage work executed on the Clarinet, which has frequently used right-hand keys of similar placement.For the thumb, I have resorted to playing with it at an angle that is more perpendicular than many other oboists use. The goal of this angle is to help keep the fourth finger near the D key. I believe this is in line with the recommendation of Ferdinand Gillet in Method for the Beginning of the Oboe where he writes: "Hold the instrument with the tip of the right hand thumb, so that the instrument rests on the right side of the nail and also on the flesh of the thumb." I'm taking the words "the instrument" to refer to the body of the oboe, not the thumb rest. This angle may be a bit painful at first, but after a while, calluses will develop on the right side of the thumb and there should be no further pain due to this angle.
With the wrist, I have added a bit of an upwards rotation, so that the middle knuckle of the index finger rests close to the A-flat key. The right thumb, as a result, does not lie straight across the bottom side of the oboe, but at an angle that is tilted towards the top of the instrument on the right side. The whole point of these two adjustments is to make all right-hand keys as close and easy to play as possible.
A bigger challenge, for most oboists, is that learning to use a new key will take a significant investment in practise time. In other words, the difficulties are not so much physical as they are training issues. Creating new habits is a time consuming task. Towards that end, I have the following suggestions:
1) Always use the right A-flat when practicing or reviewing scales or arpeggios, at least until the option feels natural and occurs automatically.
2) Carefully work through the Sellner vol. 2, starting with using the left-F in every situation where it is possible. A feature of the right-hand A-flat is that it enables more frequent use of the left F. So, we might as well train the hands to take advantage of this benefit. Once we get to exercise keys that include with A-flat, always choose the right-hand option, and work up both pure right-hand intervals (right A-flat to right E-flat or D-flat) and mixed hand intervals (right A-flat to left E-flat or D-flat).
3) If you are trying to build up Jazz technique, I'm going to also recommend working through Joseph Viola's Technique of the Saxophone, Chord Studies (vol. 2 of the Berklee School of Music Saxophone Technique series). These exercises are similar in many ways to those in the Sellner. The emphasis in this volume is to acquire technique for playing neighbor tones of a chord. The lower, upper and combined neighbor tones are presented for every chord tone, and miniature studies, which can be executed on a single breath, follow to help lock in the material.
I've been going through this regimen for about a year now (with the Viola studies started a month ago). I can't say that the right-hand A-flat is as fast yet as the left in every instance (trills between G# and F# should stay with the left-hand version), it works much better for me than using the left-hand F in passages where one can play the forked F. Despite procrastinating instead of practicing, and being almost 60 year old, this "old dog" is indeed learning a new trick and is getting closer to reaching the goal of being able to improvise on Jazz changes.
