Davidski notes in a recent post at his Eurogenes blog that two Bell Beaker individuals from the same grave, who are probably third degree relatives, have genomes that are at the opposite extremes of available Bell Beaker samples in their affinities. One has strong Corded Ware civilization affinities, while the other has strong Southern Bell Beaker affinities.
This suggests that in the era in which the Bell Beaker culture flourished in Western Europe that at least two distinct peoples with significant steppe ancestry, one of which may have been derived from the Corded Ware affiliated Single Grave Culture, and the other of which was more distinctively Bell Beaker, were in the process of assimilating into each other, even at the granular level of extended family groups. The migration routes and sources of the latter group aren't clear, although it seems to start in the European steppe somewhere and it seems to end up in the general vicinity of Southwest or central Western Europe, probably with some admixture with local populations including those with Western Hunter-Gather ancestry, en route or upon arrival.
Moreover, his observation, with which I tend to agree, is that this melting pot phenomena appears to have been going on over a large geographic area extending pretty much over the entire geographic range of the Bell Beaker culture simultaneously.
Since the end result of this process was something very close to the modern Western European gene pool that exists today, this process of Bell Beaker ethnogenesis is noteworthy.