Why do classical guitarists recommend putting the left thumb between the index and middle finger?

Question

In most of the literature that I have seen, the recommendation is for the left thumb to be roughly in line with the index finger, running parallel to the frets. I find that, especially toward the first fret, this causes excessive wrist bend. If I move my thumb closer toward the floor and angle it so that it is more of a 45 degree angle, I find it helps me keep my wrist straighter. Are there any problems associated with adopting unorthodox thumb positions?

Edit:

I've realized it's possibly some type of optical illusion. In the first picture I have my thumb low on the neck and the wrist has a slight bend.

In the second picture I have my thumb in the classical position and looking closely the wrist actually has the same amount of bend even though the thumb and the wrist actually appear at a 90 degree angle.

Answer 1

I'd say that the location of the thumb is a guideline, not a hard-and-fast law. You can move your thumb laterally a bit in one position compared to other positions if you find it more comfortable.

Classical guitar necks are very wide and fat compared to electric guitar necks, and on a classical neck it is important to keep your thumb near the middle of the back of the neck so that your fingers can reach all over that extra-wide fingerboard.

On an electric guitar neck, or most steel-string acoustic guitar necks, the neck is much narrower and thinner. In that case it's feasible to let your thumb wrap around the whole neck; for some barre chords, it may in fact be easier to grip with your thumb wrapped around the neck. Some electric guitar players even fret notes on the low E string with their thumb wrapped around. But try to do that on a classical guitar, and your hand and fingers will be so constrained by the heft of the neck that it will slow you down tremendously.

Answer 2

I think your photos exaggerate the vertical placement of the thumb. The idea is to have your left hand as relaxed as possible, but still do what it needs to do to play the instrument. If you center your thumb roughly between your middle and ring fingers, that makes it easier for you to jump up a position.

As you say, you should try to keep your wrist as straight (in all axes) as you can. If you're holding the instrument correctly, with a proper neck angle, following that rule will probably put your thumb in more or less the correct position. Your photo looks like you're trying too hard.

Relax your left hand, and hold it more or less in your playing location (but just in the open air - no guitar). Now touch your thumb to the pair of your ring and middle finger-tips. Now spread your hand open in a natural and relaxed way, so there's room to fit the neck between your thumb and fingers. This is more or less the playing position you should try for.

Anyway, like the answer above says, this is a guideline. As you reach for other positions, you will naturally change the thumb/finger relationship. But you want to try for a central, "home" position when you can. It should give you the most strength and mobility.

Answer 3

The main answer to your question, is this: learn three or four classical pieces. You will find that the position recommended by classical guitarists is one that you practically cannot avoid in order to play certain passages with maximum comfort and ease. It's an issue that will take care of itself as you find the most efficient, most comfortable fingerings for that type of musical material.

The thumb has to oppose the forces from the fretting fingers. Classical material often involves stretch fingerings, because there are independent melody lines which sometimes go quite their separate ways. The thumb has to be somewhere between the extreme points of the stretch in order to balance the forces.

The thumb position in your first picture will work okay some of the time, but it will probably not lead to a strong and confident grip for passages that require stretch fingerings.

In fact, that thumb position will not only fail to support the classical style but it is a weak one for just about anything. For example, it will not properly support a string bend when you're playing the blues. A strong position for that is on the edge of the neck, pressing down, against the upward bend executed by the fingers.