iTunes had a "brushed metal" interface - the Apple HIG said brushed metal was for apps that represent "devices", as opposed to standard "Aqua" (or "Platinum" if you go back far enough) for apps which represent "documents" - and in the top-right corner was a recessed "iris". When you put a blank CD into the drive, then clicked the iris with a playlist selected, the iris animated opening, revealing a glowing yellow and black "Burn" button (using this same icon). You clicked the glowing button and your playlist would be burnt to CD.
Burning a CD was an expensive operation (both in time and compute, as it slowed the machine down, plus it tied up your CD drive), so the "safety cover" iris and the animation revealing the button underneath used to delight me every time I used it.