Well I will not bother looking for the missing deleted docs for this component, but on SMP (x32) / JSplitter (x64) you have a callback which is called when playing a new track, which sounds to me a solution.
https://theqwertiest.github.io/foo_spider_monkey_panel/assets/generated_files/docs/html/module-callbacks.html#~on_playback_new_track
"on_playback_new_track"
I suppose the JSP equivalent is even named the same. In any case, both work for x64. You can run CMD commands there, adding this line to the callback:
new ActiveXObject('WScript.Shell').Run(command, 0, bWait);
For ex: (copy old.txt to new.txt, hide the CMD window and wait to finish)
new ActiveXObject('WScript.Shell').Run('CMD /C COPY "old.txt" "new.txt"', 0, true);
All together: (I don't think I added anything incompatible with JSP)
const WshShell = new ActiveXObject('WScript.Shell');
const command = 'CMD /C COPY "old.txt" "new.txt"';
function on_playback_new_track(handle) {
if (handle) {WshShell.Run(command, 0, false);}
}