they don't have to be together all the time to record songs.. its not necessary ..Lena can record first and then later add Yulia's voice..
Need to see the Lena singing part if it looks like successful. They as probably didn't show everything .. just the 'problem' part.. you know.. OR maybe they did show the positive part ..but the negative part already blocking our head.. like Yulia cannot scream... but they sang LIVE in Tokyo Dome.
Off topic:
Then Yulia .. awww..get well soon baby girl.. you'll be 19 ..in umm.. 20 days.... and I am here
.. for you ..
with love and tender.