The Boss PS-5 is a pitchshifter with contains several functions such as Pitch Shift, Harmonise, Detune, Tremolo Arm and Flutter. A good image and description of the PS-5 can be found here: http://www.bossarea.com/loadpage.asp?file=boxes/ps5.xml
The Balance control (and its small concentric control) vary in function depending on the mode of the pedal, and also on how you have connected the pedal.
In Pitch Shift mode it is possible to play chords and single notes. Try the same when you are in Harmonist mode and the sounds may sometimes warble a bit. The Harmonist mode on this pedal may be the weakest function.
The Detuned mode can give you a sound which may remind you of a chorus sound. It is possible to vary the amount of detuning you apply. Check my demo for this mode here:
Furthermore there is a Flutter and T-Arm function on the pedal. The T-Arm function simulates a Whammy bar sound of the guitar: You can press the pedal to mimick Whammy bar sounds, it is possible to Whammy down or up depending on the sound you would like to achieve. It is possible to recreate natural vibrato arm sounds, but it is also possible to create more artificial sounding effects. Whole step down tuning (like Pedal Steel Sound) are also possible and sound very close to the real thing. You may have to look at your playing technique to get the right feel for the pedal to sound natural.
The Flutter mode simulates Tremolo arm of guitar going up-or down and then coming back to neutral position while vibrating. Boss VB-2 does have a similar kind of sound.
Made a short video which demoes some of those sounds: