Is there any utility program for PC to play the Style files using the sound card of the
computer ?

Well, yes. It's called the REName command (from the DOS prompt), or simply rename the file using the Windows Explorer (or File Manager if you're still stuck with Windows 3.x) to have a ".MID" extension. Now play it with any MIDI player. Voila!

The only thing special about the SFF (.STY) file format from a typical Type 0 Simple MIDI Format (SMF, .MID) file is that the SFF contains Markers (an SMF-standard meta-event) that label where the Intros, Endings, Fills, Mains, etc. are, plus a couple at the beginning that tells the destination device that it is an SFF file and what version of SFF it is. You can view and edit these Markers in most modern MIDI sequencing programs, including the $30 Power Tracks Pro Audio 6.0 or later from PG Music.

The MIDI channels have specific assignments in SFF .STY files also.

Hi

Stop !!!!
Don't ever edit a style in a normal sequencer software.

A style file has Markers and the other previous mentioned stuff. But most of all:
A style file has a section called CASM at last in the file. This section holds non-MIDI data used to control the sound of style at the keyboard.

Most if not all normal sequencer software doen NOT read non-MIDI data and throws the CASM section away like garbage. This means saving a style file in a sequencer software destroys valuable control information.

Have you ever wondered why a renamed .sty to .mid file sound strange compared to the sound at the keyboard?
Answer: The sequencer or the midi file player you use for play back does not understand non-MIDI data.

What to do:
Get CasmEdit from Evgeny Osenenko. Split the style file in a midi part and a CASM part. Edit the midi part in your favourite sequencer software and then join the edited midi part with the CASM part.

CASM data can be edited too. But this sure is a very long story to tell here.
If you are interested go to the The Unofficial YAMAHA PSR 740 Home Page at http://home7.inet.tele.dk/js/musik/740pages
Follow menu: "PSR Links" -> "Style Articles" to mine and other persons articles on this subject.

There is a link to the CasmEdidt software at the page too. Follow menu: "PSR Links" -> "Software"

Jørgen