This paper presents digital models for analog phaser and flanger / chorus effects. The structure of analog phasers is reviewed. The operation of two phaser implementations is analyzed and nonlinear digital models are presented for them. The models are based on cascades of one-pole filters with embedded nonlinearities and are suitable for real-time implementation. Modifications to standard digital flanger / chorus effect are also presented. A method to warp the delay time to more closely resemble the behavior of bucket brigade delays is presented. Also a simple model for companders used in such analog effect units is presented.