In my opinion ReplayGain calculation in soundKonverter should write album ReplayGain too when processing single files. SoundKonverter does that for FLAC and Vorbis, but not for MP3 and AAC. This is desirable because many players don't fall back to per-track ReplayGain metadata if album metadata is not available. Of course, with AAC there is also this more important issue: https://forum.kde.org/viewtopic.php?t=136507