B-Keeper works by having both the click of the sequencer and input from the kick and snare microphones routed to the software, which is written in the Max/MSP prgramming environment. It looks at where the bass drum and snare are happening and changes the tempo to accomodate slight change. It also recognises fills, swing, syncopation, although it is not necessarily foolproof. Although you and I can recognise a new tempo in a couple of seconds and adapt to it, B-Keeper needs to be told the starting tempo - either by clicking sticks to bring it in, or just starting at a preset tempo. But after that, it should follow a drummer fine. The intro level on the snare is the mic level for the clicks only. In the new MaxForLive version, an option is given to automatically change the thresholds to find suitable levels.
In order to know the tempo of the sequencer, B-Keeper requires a click track.
in the new MaxForLive plugin, there are two options for how this is done:
(1). use an audio click, sent out the soundcard and routed back into Live, and using the B-Keeper click channel. (see example)
(2). use Live's internal click. This is a simple default and will work automatically. This is only available in the MaxForLive version. A toggle box allows you to choose between these two options.
Option (1) is actually preferable since it eliminates any latency from the soundcard's buffering system, but requires setting up.
Any problems please email me.
Further information about the devlopment of B-Keeper, including publications at the New Interfaces for Musical Expression conference can be found at my personal website for research.