InTime Tempo Tracking System (Win, $119) from Circular Logic is a program that its manufacturer calls “a metronome on steroids.” Instead of dictating tempo, it follows you and adjusts its tempo as you play. That may seem a little contrary to the usual purpose of a metronome (though learning to control and manipulate its tempo is an interesting practice exercise), but InTime doesn't just play clicks. It also plays Standard MIDI Files (SMFs) and generates MIDI Clock data for controlling external MIDI devices and other MIDI software running on your computer. You can select a separate MIDI routing for each of its outputs.
InTime is primarily a performance tool that lets you breathe life into the tempo or groove of MIDI sequences being played by either internal or external sequencers. If you use a sequencer to play backing tracks, InTime will synchronize the sequencer's tempo to your live playing. A little time is required to master InTime in performance, but it provides Advanced Tracking parameters to optimize its tracking of various input devices, including keyboard, wind, percussion, and guitar controllers. InTime will also record your playing, complete with tempo changes. You can save the result as an SMF and import it into another sequencer or notation program for fast scoring or tempo matching of your performance.
You can download a time-limited demo at Circular Logic's Web site (www.circular-logic.com). You can also find detailed tutorials and MP3 files that illustrate InTime's three main functions. The first uses an InTime-captured tempo map to groove a straight-ahead MIDI rhythm track. The second uses an InTime-recorded classical performance to produce a nearly flawless score. The score without InTime tempo adjustments is provided for comparison. In the third tutorial, InTime tracks a drummer while controlling the tempo of a performance in Reason. The examples will give you a good idea what InTime can do and help you determine if it's suitable for you.