Hi Dick,
the easiest thing you could try is to press the Esc button TWICE: The first Esc stops the playing song and goes to the beginning of the song. The second Esc, among other things, will reset the internal playback parameters of vanBasco (in "Control" window).
It could be even better, if you press the Space Bar first (to Stop/Pause) the MIDI file, and then press Esc TWICE.
But it would be best to Quit vanBasco completely after each song. That is what I always do. Mostly I use the shortcut "Alt + F4" (thumb and middle finger of my left hand) to Quit vanBasco.
I also recommend to check the Settings of vanBasco: Click on the "eighth note" symbol in the upper left corner of the main window (or right-click anywhere else in the main window) and choose "Setup...". In "MIDI" tab should be activated the Reset Mode "XG" (to send an additional XG Reset when a MIDI file starts), or you can activate the option button "SYSEX file" here (but leave the text box empty).
With the three check boxes unterneath, I recommend to check only the middle one ("Skip Redundant Data").
If you still have problems, you could use the "Optimize XG" feature in "PSRUTI". To do this in "Batch Mode" (optimizing all MIDI files of a folder) do NOT load a MIDI file, first.
Hope this helps!
Best regards,
Chris