Tandem is amongst the most sought after companies of Y Combinator's summer batch. : Tandem, one of the most sought after companies to graduate from Y Combinator’s summer batch, will emerge from the accelerator program with a supersized seed round and an uncharacteristically high valuation. The months-old business, which is developing communication software for remote teams after pivoting from crypto, is raising a $7.5 million seed financing at a valuation north of $30 million, sources tell TechCrunch. Airbnb investor Andreessen Horowitz is leading the round. Tandem and a16z declined to comment for this story.