Piano voting is illegal in many countries.
[1] In other countries it's legal for two legislators from opposing parties to agree to vote for the other one if one must be absent.
[3] Piano voting is a common occurrence in Ukraine, even at the parliamentary level in the Verkhovna Rada (the Ukrainian national parliament).
The Ukrainian government has attempted to curtail the practice, through disincentives like fines and the installation of sensor technology that makes it more difficult to vote for multiple people.
There have been several votes in which members of the Parliament of Armenia, mainly of the Republican Party of Armenia (RPA), voted instead of other MPs.