I already read some previous posts about this topic, but I’ll just ask: Brewing my first sour, planning a 5-6% abv with Safale 05, then in secondary add Lambic yeast and 12 lbs of frozen cherries (dumped right in) for 6 months or so. Suggestions?
Keep head space to a minimum and punch down fruit if above the beer.
Okay. And would you suggest tart or sweet cherries? I know the answer is probably preference, but that’s what I’m asking.
Tart is the norm.
Tart for sours, but I like bings in dark normal beers
Never, ever put sweet cherries in lambic.
Belgium thanks you.
I prefer Balaton over Montmorency cherries, but that is my palate. Schaarbeek cherries are almost impossible to find in the US.
Same in Belgium 
If cherries are hard to find, I have had success with tart cherry concentrate. Plus no messing with post ferment fruit pits and skins…some concentrates are pretty good these days.
I gave up looking for sour cherries where I used to live and planted a couple of trees.
They grow a lot of eating cherries in the NW.
For some reason, Michigan grows about 75% of the sour/culinary cherries.
MIchigan State has a prof that has been trying to diversify the sour cherry varieties. There are many from Hungary and Poland that have never been introduced here.