Mixed In Key is a software application designed for DJs and music producers, primarily focusing on harmonic mixing. Developed by Mixed In Key LLC, the software analyzes audio files to determine their musical key and BPM, enabling DJs to create smoother transitions and mixes that sound harmonically pleasing by using music theory concepts like the Circle of Fifths and the Camelot Wheel. Beyond key detection, Mixed In Key often includes features like energy level analysis and cue point suggestions. While it's considered a valuable tool for many DJs to organize their music libraries and improve their mixing, some argue that relying too heavily on it can limit creativity and that built-in key detection in DJ software is often sufficient.