Gag panel and strip-proper unity alert! This rare occurrence is intensified by an equally rare joke-about-modern-technology. I do like that the strip isn't reliant on iPods in specific; in 1995, it could've been about Garfield's DiscMan, or in 1989 it could've been about Garfield's new Fisher-Price Pocket Rockers. There's also no hint of the hacky comic strip trope wherein fogeys cannot comprehend the technology of today- e.g. Dagwood shooting himself in the brain because he sees a VCR.
I read Garfield every day, but I'm first to admit that the humor is low-key, if not check-for-pulse catatonic - that's part of the fun. But this punchline actually made me laugh aloud. I even like Jon's innocent excitement to find out what delightful sounds must be inspiring this reverie. This is a fat-guy joke par excellence, and there should be much back-patting in Casa Davis this eve.
Finally, in the Gag Panel, Garfield's right earbud cord is loooong.