Air carrier Captain reported while on approach the PRM monitoring frequency at ORD was active with various ATC instructions to other aircraft not on the PRM approach creating a distraction and adding to pilot workload.

Narrative

This is a continuing problem; I have seen this *many* times before. ORD was advertising ILS PRM approaches to the south runways; and we were indeed cleared for the ILS PRM 28C as were other aircraft in front of and behind us. When we switched to the PRM monitor frequency on Comm 2; either tower or ground was simultaneously transmitting on that frequency as well as whatever their primary frequency was. This leads to a dangerous situation: in my ears I've got two ATC frequencies stepping on each other when I need to clearly hear and understand what is being said on Comm 1 - and Comm 2; the monitor frequency; should only *ever* have information about a blundering aircraft. If I hear a second voice on the radio I am required to pay attention to it! Instead; I'm getting chatter about crossing runways; holding short; and follow whoever. I'll add that at this time we are also conducting an ILS approach. It's not as if my workload is low here. There are two pages in the ORD Jepp arrival pages devoted to the strict procedures we have to follow to safely accomplish PRM approaches. Somehow; ORD Tower feels like they do not have to follow these procedures when it's inconvenient. I did not question them this time; but I have in the past and was given a brush off.