FileSieve is a program which puts files into folders named after the first letter of the filename, e.g.,

Abani, Chris - Song for Night
Bach, Richard - Jonathan Livingston Seagull
Caldwell, June - Room Little Darker

becomes

A > Abani, Chris - Song for Night
B > Bach, Richard - Jonathan Livingston Seagull
C > Caldwell, June - Room Little Darker

but if say your S folder still has dozens/hundreds/thousands of files, it would be beneficial to be able to put them in folders named after the first two letters of the file, e.g.,

Sansom, William - The Body
Saravia, Alejandro - Red, Yellow and Green
satyal, rakesh - blue boy
Sloan, Holly Goldberg - Counting By 7s
Sloss, Aria Beth - Autobiography of Us
Slouka, Mark - Brewster
Swartwood, Robert - Hint Fiction
Sweeney, Kate - The O'Malley Legacy
Swift, Graham - Shuttlecock

becomes

SA > Sansom, William - The Body
SA > Saravia, Alejandro - Red, Yellow and Green
SA > Satyal, Rakesh - Blue Boy
SL > Sloan, Holly Goldberg - Counting By 7s
SL > Sloss, Aria Beth - Autobiography of Us
SL > Slouka, Mark - Brewster
SW > Swartwood, Robert - Hint Fiction
SW > Sweeney, Kate - The O'Malley Legacy
SW > Swift, Graham - Shuttlecock

FileSieve doesn't seem to do that and I've been unable to find any program which does.  So far I've been doing it by using Bulk Rename Utility to remove the first letter before using FileSieve then putting it back on with BRU after.

Many thanks.