Starting at Music Collection 2.1, the A-Z letterbar can be totally configured. Now it can show different alphabets.
5 different letter bars are pre-installed: Latin (default), Cyrillic, Arabic, Greek and Hebrew. But the new system goes beyond that: You can easily create your own alphabet letter bar without messing up delicate code. How? There's an option called "Custom letterbar".
If you choose this one, all you have to do is open the file /components/com_muscol/helpers/alphabets.php
In this file, the alphabet bars are defined. At the end of this file, you can change the characters shown (latin, by default) for you own's.
Latin alphabet (default)
Russian (Cyrillic alphabet)