You use a karaoke player. Some have that function, some don't. Several are avilable for free download. Suggest use Google.com and search for "karaoke player". I think one that does that is midi-oke player.
You can use XF Tool - a free Yamaha software. Link to the download site at The Unofficial YAMAHA PSR 740 Home Page at http://home7.inet.tele.dk/js/musik/740pages Follow "Songmaking" -> "XF Resources" in the white bar.