Spektrografi Ulla-Oda-Åse-Olga-Agnes

This image refers to video here on OMN:
http://www.overtone.cc/video/harmonics-23456-back-rounded

The organic sequence of back rounded vowels from U through A, unfolding simultaneously the harmonics no. 2-3-4-5-6.
Made with Overtone Analyzer software. The pale yellow writing and boxes I have drawn into the screenshot, to elucidate the correlations between tone, vowel sound and number. It is tempting to interprete it as a rigid structure but please don't!
At the top line the danish girls names with their initial vowels indicate the approximate sound values.