Carl Martin Ottawa is an optical envelope filter that was once popular in the Vintage Series and is a smaller optical envelope filter that has been a smaller version of the Classic Optical Envelope. In the Classic Optical Envelope, we had a foot switch to switch high pass/band pass/low pass filters with two foot switches, but it has been modified to a pin switch by making the S series. In addition to the "Q" which can change tone control, levels and frequencies, the new Attack also allows you to adjust the sensitivity of picking. The Ottawa is an envelope filter that mimics the strong and weak wow pedal sound of picking attacks without stepping on a wow pedal or manually adjusting the frequency. Whether youre not interested in disco sound from the 60s and 70s or other music that requires unique sound, this pedal is perfect for solo and rhythm work, so youll want to have it played. There are three controls: high, band, low pass filter, bandwidth and attack adjustment, level and tone you can change these to find more unique original sound.