Knowing the 'Key' of a song is essential for DJs to mix harmonically. It would be a useful and simple addition to the Sort Your Music web application using the Echo Nest track metadata.
Many times I'll make a playlist full of potential songs to put in a future mix. I'll look through the songs, find the BPM and key using a free iPhone app for DJs, and store that information in a spreadsheet. Then I'll go through that list to choose songs for the mix, and put them in an order that works (greatly considering BPM and key) before I purchase the songs.
Now I use the 'Sort Your Music' web app for BPM, which is great, but I still have to go through all the songs one by one to identify the key with the iPhone app.
Please implement this simple, powerful feature!
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