Korpa 
The Boss DB-90 Dr. Beat Metronome features Rhythm Coach functions with an onboard microphone, a reference-tone function for tuning, an instrument input, MIDI input, and other handy tools.
The Boss DB-90's note mixing function allows you to instantly create a variety of beats by adjusting the levels of 5 different note values. Front-panel sliders, buttons, and a large rotary dial provide instant, hands-on access to edit parameters. Select 4 different click sounds, plus a human voice-counting sound that will help you know your place in the bar. The DB-90 is also equipped with realistic PCM drum patterns, for developing your accuracy and rhythmic feel effectively.
Plug Into Rhythm Coach
Rhythm coach has 4 training modes to help build your accuracy, speed, and endurance. With the Boss DB-90's microphone, you can use the Rhythm Coach functions with acoustic drums or plug a Roland V-Pad into the trigger input. Play along and chart your progress.
Many Uses
Drummers can connect to the DB-90 Dr. Beat Metronome via Roland V-Pads or the internal microphone. Guitarists and bassists can directly plug into the DB-90 without any other gear required and monitor via connected headphones. And for those who wish to sync to an external sequencer for more elaborate accompaniment, they can do so with the DB-90 metronome's MIDI input. This stage-oriented feature of the Boss Dr. Beat Metronome is especially useful for drummers.
