Sometimes, it’s hard to discern how a piece of art was made. For example, the abstract circular drawings in “Current Recorder,” Billy Friebele’s show at Hamiltonian Gallery. Why are their spindly lines punctuated by round blotches of color? The answer is close at hand: The device that created the drawings sits in the center of the gallery. Constructed from found objects, which include the shopping cart that supports it, the recorder is a wind- or fan-powered automatic art-making machine. Multi-colored Sharpie pens dangle from the rotating device, sketching circles on paper when they’re in motion and allowing ink to seep into the paper when they’re not. Friebele writes that the work “gives visibility to flux and ephemerality,” invoking a very loose translation of a line from Heraclitus, the pre-Socratic philosopher. But the drawings are also lovely on their own terms, and the recorder is a nifty repurposing of urban detritus. Where Heraclitus extolled the universe’s randomness, “Current Recorder” makes the case for a little human intervention.