Searching songs with Cyrillic letters (e.g. Russian) does not discard their case. In other words, it is case-sensitive. For example, my playlist has a song titled "Ты или Я". When I search for lowercase "ты", I get no results, however when I search for literal "Ты", the song does pop up. "Т" and "т" are the same letter in lower and upper case. (See the first two enclosed screenshots.)
This behaviour has two problems:
1. It does not DWIM (do what I mean) as this sort of search is supposed to be case-insensitive.
2. It is not consistant with search in Latin charaters (e.g. English), which is actually case-insensitive. (See the last enclosed screenshot.)
Note 1. This bug has been around for at least a handful of month, I just did not get around to report it before.
Note 2. This bug concerns case-sensitivity with Cyrillic characters in particular, but not the search in general. (However, perhaps the problem spans over to other non-Latin scripts too, I haven't checked.)