Doppler will group together songs in a compilation if tags are set in the expected format.
Doppler will first check if the Album Artist tag is set and group using that (i.e. album named "Late Night Tales" by "Floating Points").
If no Album Artist is set, it will next check for the Compilation tag and group based only on the album title. Doppler will then use "Various Artists" as the album artist.
If neither are set, Doppler won’t group the songs.
Fix in Doppler for Mac
Open the Albums view and select each album you want to group. Right click the albums and select “Merge Albums”. Doppler may also ask you to enter an album artist in certain scenarios.
Fix in Doppler for iPhone
Open the Settings screen in Doppler, select "Manage Library" and then select "Merge Similar Albums". Doppler will find albums that have matching names and help you group them into a single album.