Well, yes, you do have something going on, from the look of things.
First, let’s deal with that huge image. You’re using a PNG, which gives you great image quality for the drum, which I presume you like. The PNG has transparency, which isn’t being used as far as I can see. This means that you can replace it with even a high quality JPG, and still reduce the size (and time to load that image) by something like a factor of ten. Converting to a JPG at 85 quality, I am not sure I can see any difference at all in quality, and the size is 91K, rather than 813K.
Even so, that image is not your primary problem, though it will be a standout for a visitor with a slow connection.
Your site actually runs ExpressionEngine with quite reasonable speed—try http://www.drummagazine.com/lessons/, which is nice and snappy. However, when you click on a specific post, as listed on this lessons page, you get a very long page processing time - over 10 seconds before the first return begins from the server, as Pingdom shows.
What I would do is log in on another tab to your CP, and turn on Display Output Profiling and Display Template Debugging on Admin>System Adminstration>Content and Debugging—be sure to Submit.
Now, when you reload your page on its own tab in the same browser, you’ll see a long set of extra information below the page. You might get a clue from the SQL query timings if there’s a database issue, or from the template processing step timings nearer the bottom if it’s a template code or add-on issue.
Similarly to the case of the image, I think you should be running over ten times as fast as you are for that post page—and considerably better yet with caching in place, with processing taking just a few tenths of a second or so.
Just as a tip also, it’s good to keep in mind that Pingdom always shows your worst case, downloading every detail as if a browser’s cache were empty each time. With a big delay on the primary page return as at present, though, that’s going to dominate the browser speed so that you don’t see the benefits of its caching.
Good fortune, and am sure we’re all interested what you find.
Regards,
Clive