Definition of "drum up"

From 1910, to drum up custom, the Metropolitan would operate a luxury Pullman service from Verney Junction to Aldgate.

2012, Andrew Martin, Underground Overground: A passenger's history of the Tube, Profile Books, page 73

In America alone, people spent $170 billion on “direct marketing”—junk mail of both the physical and electronic varieties—last year. Yet of those who received unsolicited adverts through the post, only 3% bought anything as a result. If the bumf arrived electronically, the take-up rate was 0.1%. And for online adverts the “conversion” into sales was a minuscule 0.01%. That means about $165 billion was spent not on drumming up business, but on annoying people, creating landfill and cluttering spam filters.

2013 May 25, “No hiding place”, in The Economist‎, volume 407, number 8837, page 74