Rock-poster collecting plucks many strings in the heart. Finding the right one celebrates that concert night you do - or do not - remember well. Other collectors seek out classic acts they only wish they had seen on stage.

At a higher level, the best posters by recognized artists - particularly those from the psychedelic '60s scene in San Francisco - are treated as fine art. They sell for thousands of dollars at major auction houses and reside in the permanent collections of museums.

This weekend is the 40th anniversary of the Woodstock music festival, which took place in Bethel, N.Y., from Aug. 15 to 17, 1969. Music fans know the iconic poster - bird perched on guitar neck. One signed by artist Arnold Skolnick sold at Christie's in New York last November for $1,000.

Local rock historian Mark del Costello, who teaches digital filmmaking and video production at the Art Institute of Philadelphia, still has his battered ticket from the event and remembers how "Santana galvanized the crowd."

"I'm rediscovering my old concerts through my ticket stubs," says del Costello, who also does archival consulting for the Rock and Roll Hall of Fame. "I saw Joplin - Big Brother and the Holding Company - twice at the Electric Factory. I saw the Kinks and The Who there, James Brown and Cream at the Spectrum." See a selection of his rock photos at delcostello.com.

As Philly boomers will remember, the old Electric Factory was a converted factory space at 22d and Arch Streets. The venue for top rock acts opened in February 1968 with seating on benches for about 1,200. Jimi Hendrix played there long before Woodstock.

Hendrix was on stage at the now-demolished Philadelphia Arena in March 1968; a poster from that concert sold for $1,250 at the same Christie's auction. The guitarist did a Spectrum concert in April 1969 and another at Temple University in May 1970, the year he died. Local collectors cherish memorabilia from these events.

Everyone remembers Woodstock because of the meticulous film documentation, first released in 1970, but music events were taking place across the country nearly every weekend in 1969. "That spring, summer, and early fall, there were 16 three-day festivals," del Costello points out.

"The big name in our area was not Woodstock; it was two weeks before Woodstock - the Atlantic City Pop Festival. Musicians said A.C. Pop was the best festival of the summer. They had a lot of acts Woodstock didn't have."

The three-day event in August at the Atlantic City racetrack may have drawn as many as 100,000 people over the weekend and included Jefferson Airplane, Santana, Iron Butterfly, the Chambers Brothers, Joe Cocker, and Janis Joplin. The only film footage that survived, according to del Costello, is a few minutes of Frank Zappa.

Artistically, however, local art for concerts could not match the standards set in San Francisco by places such as the Fillmore and the Avalon Ballroom. "The Philly posters are really lame," del Costello says. He does recommend the ones produced for the Quaker City Rock Festivals, which began in 1968 and were held at the Spectrum and the Civic Center.

The best art of the era has been on view this summer at the Denver Art Museum in "The Psychedelic Experience: Rock Posters from the San Francisco Bay Area, 1965-1971." The museum received a private collection of 875 examples and put 300 on display, including designs by Wes Wilson, Bonnie MacLean, Alton Kelley and Stanley Mouse, and Les Conklin.

"The art was so influenced by what was happening at that particular time," show curator Darrin Aldred says. "The show has been received by the public very positively for a lot of different reasons - one's own memories of the time period to an appreciation of the design and the skill that went into creating the works."

Poster prices in the marketplace depend on rarity and condition. While some examples sell for less than $1,000, masterpieces in good shape can bring five figures.

Thanks to 40th-anniversary fever, Woodstock is everywhere. Primary source material is the recently released ultimate edition of Michael Wadleigh's 1970 documentary, Woodstock: 3 Days of Peace & Music, remastered and enhanced with more acts and performances.

The best place to find vintage vinyl of the participating musicians is R&B Records, 49 Garrett Rd., Upper Darby; 610-352-2320. Owner Val Shively, who worked in the record business at the time, notes that being at Woodstock was a commercial boost for acts.

"I love the stories about the acts that did it and didn't do it," he says. "The ones that did Woodstock became famous. I saw that happen. Anybody that was on that festival sold unbelievable amounts of records."

VH1 and the History Channel have collaborated on a television rock-doc, Woodstock: Now & Then, which premieres at 9 tonight on VH1 and at 8 Monday night on History. Director Ang Lee's dramatization of one local family's experience that weekend, Taking Woodstock, will be in theaters Aug. 29.

The Road to Woodstock: A Definitive Look Back is a new addition to literature on the subject; the memoir was written by one of the festival's producers, Michael Lang. For a scholarly examination of the '60s visual scene, look for the exhibition catalog, "Summer of Love: Art of the Psychedelic Era," published by the Tate in London.

Collectors interested in the aesthetic angle should catch the new film American Artifact: The Rise of American Rock Poster Art, in which 30 artists are interviewed. Find the screening schedule at AmericanArtifactMovie.com; the New York City premiere will be Oct. 15.

Two great places to view a multitude of poster examples online are the Rock Poster Society's Web site, trps.com - "trips" for short - and WolfgangsVault.com. This sales site features not only major posters, but also rock photography and even vintage tickets.