What to do with your right thumb while playing finger style. This was inspired by a thread on another board. Hope it helps.
Thumb position, where should I rest my thumb? Good question but not a lot of new players have the nerve to ask such a thing. What I am about to post is the technique I was taught when first starting out and I still use to this day.
The best position to rest your thumb is the one that is most comfortable to YOU but will not corrupt good finger form.
What is meant by the above sentence is that resting your thumb on a pickup, thumb rest, E string or just on the body its self are all good places as long as you can still "stroke" the string and not "pluck" or "push" the string with your fingers (unless of course that is what you intend to do for a particular tune you may be playing).
One of the biggest problems I find with new players is that they tend to "brace" or "push off" with their thumb. This should not be done because it can keep you from hitting clean notes time after time and the goal, for someone new, is to be able to make each stroke ring out with the same pitch as the previous note. By "bracing" your thumb you will be inclined to stroke the string much harder then needed and if you get into the habit of needing a brace then it will be very hard if you ever need to stroke the strings by the neck, between the pickups or even over the neck. You will be limiting your self to that one hand position. It will also make it more difficult when you need to take your thumb off the E string (assuming that is what you are resting on) to play a note on it.
That is why I really do not like basses, for beginners, that have a thumb rest. Most beginners do not use it as a "rest" but a "brace". It is called a rest and that is what you should do, rest your thumb.
A good way to keep from forming this "brace" habit is to not rest your thumb at all. Practice playing with the right thumb extended out as if you were going to play some funky slap riff. Not only will this help you to keep from "bracing" but if you do decide to play some slap you will be ready to. You will also be able to stroke the strings ANYWHERE and know it will sound good (well, except maybe ON the bridge or behind the nut). Once you can comfortable playing while not resting your thumb then it will make playing while resting your thumb a whole lot easier.
Now, if you must have your thumb RESTING somewhere fine but be sure to rest it and not brace it. To practice just resting the thumb, let it sit softly on the body of the bass and not a pickup, string or rest. Start off with a 1,2,3,4 exercise on the G string but keep your thumb just above the E so it does not touch it. As you move up the strings towards the E with your fingers, let your thumb move up on the body, keeping your hand in the proper position to allow you to stroke the strings.
One thing you will notice with the above technique is that you never need to drop or raise your wrist to keep your fingers in the right position. Yes your wrist will bend in a lateral motion as you move over the strings but never closer or farther from the strings.
If you were to keep your thumb, say resting on a pickup the entire time, you will notice that your wrist will move closer to the strings as you reach for the G string which may cause you to push down rather then a smooth parallel stroke. On the other side, as you move towards the E string your wrist will raise up and may cause you to pluck the string.
Well that is my lesson for the day. Hope it helps you to better your self as a musician.
As I sit here thinking about what I just wrote I thought, "Dang, I should have done a lesson on hand position as well." Well I will leave that for another day when I am in the mode to type some more.