Talking about percents of durations I'm translating an academic paper from German into English, and am having trouble finding a noun to describe a "portion of the total duration expressed as a percent." The objects investigated in this paper are all 6-part recordings. The paper compares e.g. part 3 of two different recordings by contrasting the absolute durations of the two part 3s with "the portions of the total duration they makes up, expressed as percentages."
13 words is not an acceptable solution, and my suggestion of "percentual duration" was rejected by the authors as too imprecise, because what's being described is actually a percent value and not a duration. 
No one involved in this project is a real statistician, and we would be very grateful for suggestions re. how statisticians actually talk about things like this!
 A: One way of doing this
In your case, when you talk about percentages, you may simply use the following expression: "the proportion of total duration". Indeed, a basic google search for the definition of proportion is "a part, share, or number considered in comparative relation to a whole". For example, you could say: a large/small/...[insert any sensible adjective describing size here] proportion of total duration is ... [continue your sentence]. 
A: In your question, you use the term absolute duration to describe the actual time taken in minutes and seconds. You could contrast that with the term relative duration to describe the length of time with respect to the total time. You may want to explicitly define the term somewhere in the manuscript, with just one sentence stating that "Relative duration is calculated as the proportion of the total duration, expressed as a percentage." From then on, you can use the term relative duration as a concise yet precise way of expressing your intended idea.
