I foudn out in my experance that that hotcommand dont work
here is why:
/cast 1
/pasue ( casting time)
these first two commands work well togeather it works fine after that it gets confuseing. since your singing the song you will have to stop the song. so...
/cast 2 would stop the song
/pause (casting time) you would end up waitting the next few seconds for the next song to cast
/cast 3
/pause (casting time) these would work properly
/cast 4
/pause (casting time) these again would be screwed up cuse aigan your stoping the origianl song.
if you want to do a hot key it would work more like this
/stop song
/cast 1
/pause ( casting time)
/stopsong
/cast 2
and since that is allt he spaces you have you would have to make a second hot key similur to the one above
just my experance