Hi everybody.
I’d like to clear up some confusion regarding the (3 4) combination, much of which I’m sure comes from my own failure to communicate these ideas clearly in my past threads.
First, I want to say that I believe that there are contexts where the using the (3 4) combination is valuable, and even specific situations where the (3 4) combination is the best feasible option. I do not advocate that anybody discard the (3 4) combination entirely. I never have and I’m sure I never will.
It is, however, a simple anatomical fact that fingers are not independent of each other. No amount of training can overcome our anatomy. There are limitations on what our hands are capable of due to our anatomy. As we move towards the limits of our own anatomical potentials, it becomes necessary to acknowledge those limits.
The (3 4) combination suffers because the 3rd and 4th fingers are strongly dependent on each other and because of the relative difference in finger length. In most fretting postures, using the 3rd and 4th fingers together requires that the 3rd finger be flexed significantly more than the 4th finger (4th finger significantly more extended).
The finger flexors are not independent. In particular flexor digitorum profundis, which is the sole flexor of the distal interphalangeal joints (DIPs) is a mass action muscle. We cannot flex one of our DIPs without the engagement of the full group.
If we adopt a fretting posture where the DIP of the 3rd finger is flexed, flexor digitorum profundis is necessarily engaged. The 4th finger has a dedicated extensor (extensor digiti minimi), which must engage to create the relative difference in extension in the 4th finger.
Extensor digiti minimi must constantly pull against the strength of the engaged flexor digitorum profundis. Extensor digiti minimi is a small, weak muscle, while flexor digitorum profundis is the strongest muscle of the forearm, and the muscle chiefly responsible for gripping strength.
In most fretting postures, using the (3 4) combination creates a higher baseline of tension throughout the hand and forearm than other combinations.
Now, to move the fingers to make fretting actions, we must alternate between flexing the 3rd finger while extending the 4th finger and extending the 3rd finger while flexing the 4th finger.
The flexor digiti minimi tendon fuses to the extensor digitorum communis tendons of the 3rd and 4th finger. The result is that this alternation demands constant muscular engagement, against an already heightened background of muscular tension. This is unsustainable and results in extensor fatigue very quickly.
The greater the relative length difference between the 3rd and 4th fingers, and the greater the anatomical dependence, the more severe this problem becomes.
It is possible to adopt a fretting posture which reduces this issue noticeably. This is done by “skewing” the fretting posture so that the tips of fingers (as much as is possible) point “along” the string towards the bridge rather than inline with the frets.
This posture is very noticeable in Paul Gilbert’s playing, and I’ve noticed that @Pepepicks66 who is also very comfortable with (3 4) combinations tends to default to a heavily skewed posture also. It’s also somewhat similar to a fretting posture used in much of Allan Holdsworth’s playing. It’s certainly not wrong, but it does have some very definite disadvantages also.
In addition to this particular posture, Paul Gilbert has significantly larger hands than I have. Reliable measurement indicates his 3 to 4 length ratio is about 1.1, while mine is 1.3. This seems a significant variation to me.
I’d also like to clarify that the (3 4) limitation most clearly manifests when alternating between the 3rd and 4th finger to perform new fretting actions, therefore demanding that the fingers move simultaneously in opposing directions. Most players who favour (3 4) combinations simply do not do this, with most fretting sequences involving either lifting/pulling the 4th finger to “reveal” a note of the same string that was previously fretted by the 4th finger, or sequences which do not involve simultaneous opposing movements, as @Drew discussed above.
If anybody has any questions or comments regarding my thoughts or findings on these issues, I’m happy to address them.