Thanks for the question... each one keeps me on my toes thinking about bass playing.
All bass players have this issue. But, first, WHY is it important that we bow "straight across" (perpendicular to) the string? Well, for one thing it allows us to get the most vibration out of the string. You see, the bow is not only grabbing the string and pulling on it, then releasing it hundreds of times a second - so that it can vibrate, it is also capable of - and does to some extent depending on weight and angles, interrupts the string's vibration! So not only does the bow excite the string it can dampen it. The angle for maximum vibration is perpendicular to the vibration. In addition, the angles help to bring out various harmonics in the sound. So the more close to a 45 degree angle across the string, the more the fundamental of the string is going to be lost and the harmonics will become more present.
Okay, 'nuf said about why. Now how:
I imagine there is a track that the bow must travel within, as you pull down and up bow(s). This helps give you a mental picture that your body/arms can work on. Of course other feedback, like in the mirror or video can give you a perspective, but note that the angle of the visual sighting can lead you to some physical contra-indications. When you are straight-on with the mirror, because of the curve of the bridge, the angles viewed that the bow is traveling may not look right on the G and E strings, even though it looks fine on D and A (not to mention it is "easier" on the D and A to bow directly across). I have an exercise (that I will post on YouTube some day) that focuses on the right arm's elbow, its rise and fall when crossing strings... keeping the hair flat on the string as you come across, not changing any angles. If you focus on this rise and fall, with no twisting of the wrist, you find that the bow will travel perpendicular to the string throughout the arc.
Another aspect of your technique that has a direct effect on the bow angles is your stance. If the bass is at an angle to your body, it will effect the travel of the bow. So be aware how your body's approach to the bass allows your arm to swing in certain angles in relationship to the ground. Generally our arms like to travel in an arc with regard to gravity, so be aware that you need to position your bass to accommodate this "need" of the arms. This means the fingerboard should be at the proper placement for the left arm to travel it without straining to change the "natural" travel path, and the right needs to be able to swing easily in front of your body, with the bass being "in the way" of this travel route (the strings of course). Whether you sit or stand, you need to approach the bass so that the arms can freely travel great distances. Sometimes one cannot admit that the bass is too big for one's physique, or sometimes one relies on the ease of left hand fingering over the requirement of angles and travel of the bow (this "one" was me many years ago). So, it'd be good to get someone to observe your playing and see if the approach is it, or whether you simply are not controlling the movement of the bow in its "track."
Originally Posted by A Spotless Mind
Hello Mr. Neher!
I just wanted to bring up the whole issue of bow angles. Lately I've been having some trouble keeping my bow straight (I play french by the way) and in the same place all the way across the string (ESPECIALLY the G string). I've tried just sitting in front of a mirror and play open strings, trying to keep the bow straight and keep it from moving around but it doesn't seem to be helping. I don't know if there is actually anything you could say that might help me but if you there is, it would be greatly appreciated.