Post processing summarized data

I have the following search which outputs summarized data in 4 hours chunks perfectly:

source="MySocket" NOT ServiceName="Private Service"| eval search = if(eventtype="search",CounterValue,0)|eval browse = if(eventtype="browse",CounterValue,0)|eval tracks = if(eventtype="tracks",CounterValue,0)|eval play_seconds_val = if(eventtype="play_seconds",CounterValue,0)| eval play_error_val = if(eventtype="play_errors",CounterValue,0) | eval play_error_adj_val = if(eventtype="play_error_adjusted",CounterValue,0)| eval play_errors_total = play_error_val - play_error_adj_val | eval browse_errors=if(eventtype="browse_error",CounterValue, 0) |  eval search_errors=if(eventtype="search_error",CounterValue, 0)| eval other_errors = search_errors + browse_errors|bin _time span=4h | stats sum(search) as Search sum(browse) as Browse sum(tracks) as Tracks sum(play_seconds_val) as PlaySeconds sum(other_errors) as OtherErros sum(play_errors_total) as PlayErrorsTotal distinct_count(HouseholdId) as Households by _time ServiceName

However when I try to use HiddenPostProcess with this to generate different charts and single value fields I am getting invalid field errors.

Here are a couple examples of what I am trying to do with prost process: stats sum(Households) - this is for a single value field it fails saying illegal timechart span=1d sum(play_seconds_val) by ServiceName useother="f" - for a chart, produces no results timechart span=1d PlaySecnds by ServiceName useother="f" - for a chart, errors saying it must be in the form <func>(<field>)

I cannot do the summarization step in post processing because the search will return more than 10,000 results. Does anyone have any idea how to accomplish this?

Thanks in advance, Keith