The Washington, DC area will be host to some terrific acoustic music acts during the month of May, ending with a stellar lineup at DelFest over the Memorial Day weekend.  With the coming of beautiful spring weather, this is a perfect time to hear some live music. Regular readers know that I’m a big fan of the Monday Night Concerts of the Institute of Musical Traditions.  The 2008-2009 season wraps up in May, but not before a May 4th concert in celebration of Pete Seeger’s 90th birthday (I bet they’ll be some righteous sing-alongs) and the final DC-area concert of the Canadian band Tanglefoot on May 11th.   According to the IMT website, Tanglefoot is “Stan Rogers meets Van Halen.” For some straight-ahead traditional bluegrass, check out the DC Bluegrass Union’s Spring Concert on May 9th with Dan Paisley & Southern Grass. Then over the Memorial Day weekend, all bluegrass lovers in the Mid-Atlantic region will be heading to Cumberland, Maryland, for the second annual DelFest, hosted by the Del McCoury Band.  There’s a stellar line-up, including Old Crow …