Old FM tracks with the 'tron:
The Ghost - it's what plays the flute-but-not-quite lines
Sunny Side Of Heaven - I can hear some mellotron strings towards the end, but it's buried so badly in the mix that you can barely hear it. Shame.
2nd track on Penguin - Title escapes me, it's the only one I really skip.
This also does the flutey sounding stuff in the background
Night Watch - The atmospheric, eerie string stuff predominantly for chords on the chorus and those single-note string lines during the long middle section. In my opinion it's what makes the song, even though it's already a great song to begin with. Night Watch is really suited for a mellotron part.
I can't recall hearing it on any of the other Welch stuff, and believe me I would have noticed because I'm a mellotron nut.
I really think they should have used it more, but to be honest it doesn't seem like an instrument Chris would like. She doesn't really seem like she knew how to play it. The Ghost is a great song but her mellotron part on it is nothing short of agitating. It's way too busy. The mellotron isn't an instrument you can be "busy" with. I'm not even so sure she played it on Night Watch, which credits the involvement of a 2nd keyboardist. If she did she handled it much better that time.
But really they should have used it more. Every time I hear the song Future Games, whenever it gets to the part in the buildup during the end where the bass just really slams in I always want to hear that mellotron choir just come blasting through the speakers. It would have helped Woman Of A Thousand Years immensely too. I also crave to hear the 'tron strings on the gorgeous Caught In The Rain and Emerald Eyes too.
Maybe someday after I get my EMU Vintage keys I'll record the mac tunes on my 4-track and pipe in the mellotron parts myself!
Thanks for the link BTW.