Here's something for string quartet. As you can see from the title, this took a couple of years to complete, the problem being that I came up with three different treatments of the same idea that starts with rising fourths, and after trying to pick which I liked best, I finally decided on just throwing them all together, and since the idea itself is rooted in D (more quartal than major or minor), I used an A7 chord to punctuate the three sections, and also as an introduction. The first part has half notes as the fundamental unit, the second goes to quarter notes, and the third to eighth notes, so each section gets faster even though the underlying tempo doesn't change. This piece is also a demonstration of my belief that the string quartet is an inherently contrapuntal genre. Sure, you can write for string quartet without using counterpoint, but it seems kind of a waste.
The background image is courtesy of Lynn at 4Artseasons; it's a pecan tree, chosen for the color, and for the three pecans representing the three sections of the piece.