Macworld may just have a small-business life after all. One of the odd dualities at this year's last-ever Macworld Conference and Expo here in San Francisco is that while Apple ( AAPL) itself seems to be struggling, the larger ecosystem of smaller companies that build stuff to work with Apple gear is doing just fine. Steve Jobs may be ill. Rumors are circulating about a lack of management succession plans at the company. But you wouldn't know it from the other interesting operations here building terrific products. The fascinating part of all this cool Apple stuff is how deep and wide the swath of third-party development is for Macs at this point. And though the market share of these operations remains tiny compared with Microsoft, there is a palpable feeling of growth here that uncertainty at Apple does not seem to be stopping, at least for now. Here are my picks for the most interesting products by or for small businesses at this year's show: Ocarina from SMULE, $0.99. The most clever item at this show by far is from tiny Menlo Park, Calif.-based SMULE. (That's short for Sonic Mule.) SMULE, whose founders partially came from the Center for Computer Research in Music and Acoustics at Stanford University, essentially turned an iPhone into -- get this -- a musical instrument. Its recent product, Ocarina, turns the iPhone into a '60s-era sounding ocarina, an ancient flute-like wind instrument. Basically, users blow into the iPhone microphone and the SMULE software turns that audio signal into an ocarina-like sound. Better yet, the software turns the iPhone touch screen into a virtual keyboard that can play all the tones of the instrument. And the effect is surprisingly realistic. Blow. Finger. And out comes "Proud Mary." It's terribly cool. The bottom line is, if you have an iPhone, you probably have a buck to spend. And you owe it to yourself to download this app and give it a test whistle.