Nothing succeeds like nostalgia when it's pledge time on PBS. "Echoes of the Big Bands With Merv Griffin," airing tonight at 8 on KCET and KOCE (Channels 28 and 50), is ideal for those older viewers whose pockets are well enough lined to guarantee hefty donations.
The title is something of a misnomer. "Echoes of the Big Band Singers" would have been a closer call. You see Merv Griffin, who kiddingly opens the two-hour show with a mock introduction of the Freddy Martin Band in which he sang, but Martin's band never appears.
The Harry James Orchestra is there in a couple of old black and white clips, but two James' band vocalists that are seen, Helen Forrest and Dick Haymes, have five songs between them. Similarly, Herb Jeffries gets far more time than the Duke Ellington Orchestra, and the Dorsey Brothers segment is devoted to a parade of singers--Bob Eberly, Helen O'Connell, the Piped Pipers, Connie Haines, Jack Leonard.
The program in effect reminds one of the thin line that separated big band music and jazz from dance music or simply vocal entertainment. In several instances the performers are seen in black-and-white scenes from the 1930s or '40s, followed by longer passages showing the vocalists in the 1970s or early '80s, in color, backed by a house band at Roseland or some other ballroom.