Blue CH-2s is a chorus effect, and part of the Blue Tube bundle.

The Blue Tubes Bundle is a collection of 16 plug-ins processors for PC and Mac OSX.
Designed to improve the quality of digital sound recordings. This bundle recreates the warm sound qualities of classic analog hardware. The sound quality of Blue Tubes is nothing short of amazing. Yet all 16 plug-ins provide a simple and functional “vintage-style” interface, as well as low CPU consumption for lightening-fast processing

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01) BT BrickWall BW2S
02) BT Chorus CH2S
03) BT Compressor CP2S
04) BT Compressor FA770
05) BT Deesser DS2S
06) BT Driver DR2S
07) BT Equalizer PEQ2A
0 BT Equalizer PEQ2B
09) BT Equalizer PEQ2C
10) BT GateLimiter GL201
11) BT Limiter LM2S
12) BT Long Delay LE
13) BT Oilcan Echo TLE2S
14) BT Phaser PH2S
15) BT Stereo Imager
16) BT Tempo Delay 3D