There is no program that takes any midi file
sequenced by xxx and makes a style for immediate use.
When creating a style from midi file then
1. more midi files are required, one
for each variant (e.g. Intro1, Var1, Var2, Fill1, ...Ending2...).
Korg i-series allow up to 36 variants
which are chosen depending on selected variant and on chord type.
Each part midi file has up to 6 tracks, one
for each instrument (drum, perc, bass, acc1-3) where the channel numbers must be correctly assigned (drum=10...acc3=14).
Only one tempo setting is allowed per style,
must be identical in all parts.
The var1-4 parts must all be usable for looping, because styles always loop.
Then you need a program to convert the correctly formatted midi files to style.
There is commercial EMC Styleworks at tastenshop, and currently a DOS shareware demo for a Win95 style converter available
probably in jan 99 (
http://www2.iicm.edu/korgprog)
For midi song files you can only copy and past parts from midi file into some of the midi style track files.
Often this will not be enough (e.g. a midi song has only one intro and ending, if you want that second also works, must invent a new for the style).