Adobe Audition has a "Stereo Field Rotate" effect. Might be worth a shot.

Encode the track to Mid-Side. High-pass filter the Side channel. Decode it back to L-R stereo.

Boswell wrote: Encode the track to Mid-Side. High-pass filter the Side channel. Decode it back to L-R stereo.

Bowed strings have oodles of harmonics. I wouldn't expect HPF on the side mic to center the whole instrument - just the bottom end of it. Might be a strange effects. Also, if a lot of the bass is in the side channel you might be cutting the level significantly with this technique.

It's easy enough to try - I could be wrong, of course.

you could just bring in the image a little too.

zemlin wrote:

Bowed strings have oodles of harmonics. I wouldn't expect HPF on the side mic to center the whole instrument - just the bottom end of it

Yes, exactly. However, bassists in acoustic folk trios invariably play pizzicato, and there is little harmonic energy, so the bottom end centres quite well using this technique.

There's also a free VST plugin that uses this method: http://www.otiumfx.com/basslane.php

You do have to adjust the levels and maybe the EQ after the effect. The overall width can be reduced by lowering the side level and raising the mid level before decoding.

Some of the greatest folk-type recordings I've ever heard had the bass off-center.