Thanks very much for your reply but I’m still a little confused about how to implement your workflow. Could you perhaps explain it with reference to these parts of the icon:
The background is a rounded square with the shading applied using the mask tool:

This is overlaid with one of the symbols I want to use; here, a phone:

I’m wanting the phone to have similar shading to the lettering in the sample I originally referred to (hadn’t realised before that I could have embedded it!):

Sorry if I’m being a bit slow in picking it up but my current long hours are taking their toll; one of the ‘perks’ of being self-employed 😉
Thanks again,
Ewan