Smoothie is a macOS helper application, intended to be used with the Traktor Pro DJ tool.

While mixing, it automatically suggests tracks for you based on key and tempo of the playing music.

Please note: Smoothie was developed based on version 2.6.8 of Traktor Pro. Unfortunately, I was not able to test it with more recent versions so compatibility is not guaranteed.

How does it work?

Unfortunately, Traktor Pro does not provide developers with useful capabilities to create plugins or extensions. However, it is possible to obtain a small amount of information, which is used to power Smoothie. The Traktor software writes all of its collection information (like track or playlist data) into a “collection file”. This file can be located and is used by Smoothie to gather necessary track information. If you stream or drag a song into Smoothie, it will look through this information to discover matching tracks.

What is the streaming feature? How does it work?

As mentioned above, Traktor Pro does not offer external applications any information about what is going on inside of Traktor. However, it has a streaming functionality, which gives the user the option to send out the currently mixed music in an audio stream. In addition to the audio data, every time a new song comes on, a very slim amount of metadata is transmitted as well, namely title and artist of the current track. Smoothie is able to receive this stream. It will ignore the audio packets and look at the metadata, which automatically updates the track in Smoothie and will show new matching tracks.

It would be great if Smoothie adjusted the tempo to the BMP tempo of the mix, not the original song tempo!

I absolutely agree. Unfortunately, real-time data like this is not accessible from outside the Traktor application, as mentioned above.

I changed metadata / added a file in Traktor, but it does not appear in Smoothie!

All track information and metadata is stored in the “collection file”. Smoothie loads this data while launching, Traktor saves data to this file upon quitting. So if you modify the data or add some tracks, it will not appear in Smoothie until both Traktor and then Smoothie have been restarted.