When fingerprinting files on a CD Picard will fork a fpcalc process for each currently selected track to run in parallel.  On a CD drive this will cause the drive head to seek between the multiple tracks slowing down the fingerprinting process significantly.  It would be nice to have an option to specify the maximum number of fpcalc processes to run simultaneously or an option if fpcalc is being run on a CD drive to only fork one process at a time.