Manual analysis c/o MW.  Thank you!

Original file is called YYMMDD_xxxx.flac.

MW then split into 15sec WAV files and removed noise
by using a band pass filter of 1500 to 7500 Hz. 

    sox 200928_0125.flac 200928_0125.wav sinc 1500-7500 trim 0 15 : newfile : restart

Output files called YYMMDD_xxxxnnnduet.wav where nnn is the nnnth 15s segment.

MW's analysis was as follows:

200927_0122015duet.wav     Com pip     4877Hz    

           
200928_0124009duet.wav     Com pip     4682Hz               
200928_0124020duet.wav     Sop pip     5300Hz               
200928_0124022duet.wav     Sop pip     5300Hz   

            
200928_0125004duet.wav     Com pip     4829Hz               
200928_0125011duet.wav     ?Com pip     Noisy                
200928_0125013duet.wav     ?Com pip     Noisy                
200928_0125017duet.wav     Com pip     4784Hz               
200928_0125020duet.wav     ?Com pip     Noisy                
200928_0125022duet.wav     ?Com pip     Noisy                
200928_0125023duet.wav     ?Sop pip     5533Hz clearest call 
200928_0125031duet.wav     Com pip     4394Hz               
200928_0125035duet.wav     Com pip     4662Hz               
200928_0125056duet.wav     Com pip     4716Hz               
200928_0125078duet.wav     Com pip     4664Hz               
200928_0125103duet.wav     Com pip     4680Hz               
200928_0125113duet.wav     Com pip     4718Hz               
200928_0125123duet.wav     Com pip     4718Hz               
200928_0125138duet.wav     Com pip     4658Hz               
200928_0125161duet.wav     ???Noctule     2408Hz               


UTC timestamps on the original FLAC files, as reasonably accurate start times:

27 Sep 18:11 200927_0122.flac
28 Sep 18:05 200928_0124.flac
28 Sep 18:14 200928_0125.flac