A couple weeks ago, I brewed my first true lambic. In addition to an extended boil and a turbid mash, I also planned on using wild yeast to supplement the Wyeast cultures.
I pulled off enough wort while transferring to the carboy to fill a 12oz. jar. I covered it with a fine mesh bag to keep out any bugs, birds, etcetera and left it outside for a few days.
On the 3rd day I already had signs of activity. I smelled and tasted the wort and it seemed fine, so I left it for a couple more days just to make sure nothing too gross was growing in the jar. On Tuesday, I noticed the yeast had slowed down and the krausen was beginning to fall. I took a final taste test - it smelled fainly lemony, with a bit of a woodsy, funky, earthy smell that I can't quite describe. It had an otherwise unremarkable, fairly neutral taste as well. Since I didn't see any red flags (mold, vomit smells/tastes, and such) I went ahead and pitched it into the carboy.
The wild yeast seems to have kickstarted a second round of fermentation, with the same smells that I got from the jar. I don't know if I managed to capture any wild bacteria/brett, but I'm hoping that I did. I won't know if this was a good or bad idea for at least a few more months, so I will try and taste it every few weeks and make sure it is progressing nicely.