Abbreviation for CD Recordable. These are Compact Discs that can be “recorded” by end users as opposed to standard Compact Discs, which are manufactured in factories with the data embedded in them. Recordable CD’s work in a fundamentally different way than manufactured CD’s, and this tends to cause increased problems with compatibility and reliability. Nevertheless they have become one of the standards for low cost data storage, and have likewise become a very convenient medium for working music and production ideas. Most musicians don’t exchange cassette tapes anymore, in favor of CDR discs. The basic building blocks of CDR media are cyanine dye, which is cyan blue in color, and phthalocyanine dye, which is more or less colorless. The reflective layer is either a silvery alloy, the exact composition of which is proprietary, or 24K gold. There are gold/gold, green/gold, silver/blue, and silver/silver CDR’s. The apparent color is determined by the color of the reflective layer (gold or silver) and the color of the dye (cyan or colorless). For example, green/gold discs combine a gold reflective layer with a cyan-colored dye, resulting in a gold appearance on the label side and a green appearance on the writing side. The reason why there are multiple formulations is that the materials and process for each are patented. If a new vendor wants to get into the CDR market, they have to come up with a new combination of materials that conforms to the Orange Book specifications. Discs using the cyanine dye tend to have a wider tolerance for varying laser intensities, but the theory is that discs made with phthalocyanine dye will last longer. Of course CDR longevity is a hotly debated subject itself with few agreed upon facts. Discs using silver reflective layers are reported to have better reflectivity (gain) than gold discs, as well as better heat transfer when burning, but gold reflective layer discs are supposed to last longer. The gold discs also cost more to manufacture.