Detecting Keys

In general there are 2 ways to automatically detect keys using Rapid Evolution. You can detect keys from files or use the live audio input key detector. This section will explain how to do both.

While automatic key detection is convenient, it is not 100% accurate and it is recommended that you confirm your song keys by ear using the MIDI keyboard provided by Rapid Evolution. If you are unfamiliar with how to do this, you can read up on music theory and how to find a song's key. Automatically detected keys will be assigned an accuracy value that is a rough approximation by the algorithm. When manually confirming a song's key, the accuracy value should be raised to show confidence in the information.

Before detecting keys from files, you should be aware that there is a setting which affects the accuracy and performance of the algorithm. It is located under Options→Audio:

If you have the patience and your machine can handle it, you can put this at the highest quality setting (which is roughly 5% more accurate). Here is a table which gives you an idea of the accuracy difference between the lowest and highest settings:

There are a couple way to detect keys from files:

This is the recommended way of detecting from files. To do this, simply highlight a group of songs in the search table, then right/option click and select detect→key:

You will be prompted whether you wish to overwrite any existing values.

You can also detect keys from files individually via the song properties:

When prompted, select “file”:

This is convenient for detecting keys from vinyl and other audio sources, including unsupported file types. The live key detector can also be used while mixing to determine the current key.

First, you will need to make sure the audio recording input settings in your operating system are set such that the incoming signal can be picked up by Rapid Evolution, please refer to the live audio input setup page. Then, you can use the key detector on the main screen or in the song properties dialog to detect the key.

You can enable the key detector from a couple places:

This is useful if detecting the key while mixing, as the detected key will be made the current key which will affect search table results.

When clicking the detect button here, you might be prompted whether to detect from file or live audio input:

After you enable the key detector, Rapid Evolution will begin to display the detected key. The displayed key represents the most prominent key in the audio signal from the time the key detector was enabled. The longer you let it run the more accurate it should become, and it should also settle on a particular key. It is important to stop and start the key detector if you are detecting the key of a new song or source.

It is often useful to enable the live key detector during a part of the song which is strong in melody and harmony, as opposed to a beat oriented part of the song. Generally it is not necessary to leave the key detector on for the entire song, as the key should eventually converge to a prominent value. Keep in mind, depending on your audio input settings if you play along on the keyboard while detecting then you are affecting the results!