Usually for combos I choose fibers that have a similar color tie-in that I want to highlight, and I choose wools to use that are similar in texture (for instance, Merino with South African Fine, or Polworth and Targhee.) For the Tour de Fleece recently, I thought about a combo featuring two very different textures - super-soft South African Super Fine, and Fine Romney.
Romney typically has a staple length of around 7 - 9", while the finer fibers can be as short as 2 - 3"! That's a big difference. My thought was that the colors of the two would look good together (both fibers had beautiful dark purples), and maybe the Romney would add shine and the SASF would add some softness. When experimenting with something this different and unusual, I always like to do a little test skein, so that's what I tackled with this project -- I spun up a skein big enough to knit a few swatches from, but barely enough to decrease the quantity of either fiber, just in case I didn't like the results.
As you can see from this photo, the finished yarn looks a bit hairy. This is because of the Fine Romney being a bit course, and having fuzzy hairs that stick out from the single. These fibers are what increases the 'prickle factor' and makes yarns scratchy. The ply that is the SASF looks smooth and matte, while the Romney is shiny and richer in color. In the skein, this yarn didn't feel very exceptional.
I wound it into a little ball (tiny Totoro for scale) to knit some swatches from. While winding, I felt that the texture of the yarn compared a bit to something like Brooklyn Tweed Loft or any Shetland tweed yarn that has a rougher hand. The ball itself felt springy and light.
The swatches themselves turned out... okay. The all garter stitch swatch reminds me of other rustic yarns, while the stockinette is beautiful and smooth, with jewel-tone aspects and a glowing appearance (mostly due to the Romney.) Unfortunately, I didn't feel that the end result was anything exceptional, and it certainly didn't show off the qualities of either fiber. Romney can be so beautiful and bright, but these characteristics were dulled by pairing them with the South African Super Fine. SASF is one of the softest fibers in the world, but you couldn't feel this next to the coarseness of the Romney. In the end, while it was an interesting experiment, I decided to spin these on their own.