Line is the most basic element of design. All works incorporate line and many artists begin with a simple line-drawing (sketch) to work out the idea. There are many aspects to line including orientation (vertical, horizontal, diagonal), type (geometric, organic), style consideration (straight/Classical, curved/Romantic), how thick the use of line is, as well as whether the line is actual or implied. Line is also very important in determining shape.
In music, line best correlates to melody. The melodic line is one that can be visualized just like line in the visual arts. The curved line is more like a melody that is conjunct, while a jagged edge is more like a disjunct melody.