Parmastahir, do you know if those illustrations are from an Australian version of
The Hobbit? If so, I might be able to find them online - I have found a wonderful
site with illustrations from from various international editions of the book. It has several very interesting pictures of the instrument-playing Dwarves there.
If nothing shows up online, I will most certainly contact you for those illustrations - thank you! As to "when" - no hurry yet; the lecture will be held at the Tolkien Seminar in April here in Germany.
Yes, in the book Oín and Gloín are not mentioned as playing an instrument, so it will be interesting to see how they are portrayed. I always wondered if they might simply have been unmusical!