How do I find the key
Finding the key of a track is easy if it’s on Beatport- click the search button by the track name and a new window will open with a Beatport search for your track, you’ll find the key there. Otherwise, you could use a key-detection software like Mixed-In-Key. As of yet, no site with an adequate catalogue of electronic music has an API for accessing the key of a track.
Harmonic mixing
Mixtool uses the circle of fifths to find tracks that will mix in key with the key of the track you enter. For each key, there are four keys that will mix harmonically. Those keys are displayed to the right of the key pullodown menu on each track. When harmonic mixes are displayed, you will see the type of harmonic mix: same key, key up, key down, or major-minor.