I must point something out though: if you are going to do a stereo in-line recording of the show, you’re going to come out with only two channels to work with. And that means your only way of removing SFX is with the Karaoke effect which will attempt to remove voices and such but will likely leave voice artifacts behind and will also render the audio mostly, if not totally, mono–and that is especially if you do a recording. If you were able to get the audio directly from the source, you might have better luck with the Karaoke effect, but it would still come out in mono.
Although I wouldn’t expect much better results if any of the show is/was ever available on DVD; it would be too old for there to be any reason that it might be available in 5.1 sound….Good luck anyway!
That’s what I plan to do, despite the outcome being less-than-clean audio.
There’s some other Arthur songs on this site, plus a load of other stuff!