What key would this song be in, if I played it a little slower?
beaTunes 5 will contains some neat features to help DJs mix harmonically. In the View -> View Options dialog, you can now find two changes. The first having to do with the way artwork is displayed (size and height). That one is pretty self-explanatory. But the second one, in the lower left corner of the dialog, may not be so obvious.
The new SYNC-button let's you change how a song's key is displayed, if both key and BPM are available. Assume you have a song in C major with a tempo of 100 BPM. When you press the SYNC-button and set the tempo value to 94.4 BPM, beaTunes will display the key the song would be in, if it was played at 94.4 BPM (without key lock). In this case B major. This feature is meant for DJs who prefer not to use key lock, but rather play tracks slower or faster to match both beat and key. In this context, beaTunes serves purely as a discovery tool. It does not support changing the playback speed in any way. Apropos discovery tool: the matching songs panel now offers a SYNC-button as well. This means you can easily find songs matching harmonically at the tempo of the selected song (if your ruleset contains the matching key rule).
I hope this feature proves useful to a lot of working DJs out there.