In 2011 and 2012, fans of the ’70s hard rock band Foreigner got a disappointing surprise when the band showed up at stops on its tour without a single member of the original band.

Foreigner founder, guitarist and sole original member Mick Jones was recovering from heart surgery, but that didn’t stop the show.

When the Gretna Heritage Festival presents The Guess Who and Lynyrd Skynyrd as part of this weekend’s festival with music on six stages, the classic rock-era bands will do better than that. (Foreigner is not performing at the fest.)

The Guess Who will feature two original members and Skynyrd will have one, though it also has the brother of original singer Ronnie Van Zant, Johnny.

This isn’t a new phenomenon. Individual members have taken old R&B vocal groups on the road for years, and in the 1970s, multiple versions of The Coasters toured the country.

But Skynyrd and The Guess Who are part of the first generation of rock bands to face middle and old age onstage that wrote, played and often produced their own songs. Their appearance raises a question: How many original members should be in a band to use its name? When should the band’s name have an asterisk added or appear in quotation marks in the spirit of truth in advertising?

A recent Facebook conversation chewed on these questions, and there was vague consensus around 50 percent, maybe even a little lower if it’s the right 40 to 50 percent.

Fans look for singers, songwriters, the people who did the things that gave the songs their personality. The Guess Who have the original bassist Jim Kale and drummer Garry Peterson, but not founder Chad Allen or guitarist Randy Bachman.

The Guess Who complicates the question because its original lineup isn’t the one that cut the band’s defining songs. Keyboard player Burton Cummings joined in 1966, and it’s his voice heard on “American Woman” and all the band’s biggest hits.

Lynyrd Skynyrd’s lineup changed forever in 1977 when singer Ronnie Van Zant, guitarist Steve Gaines, and backing vocalist Cassie Gaines were killed in the band’s plane crash on the way to a gig in Baton Rouge.

But there’s clearly a market for bands that carry on past their prime, so why not replace and reload? It’s not like musicians develop fall-back strategies and secondary marketable skills. If Skynyrd guitarist Gary Rossington wasn’t playing “Sweet Home Alabama,” what would he be doing? Your taxes?

The nature of the replacement matters. Chris Chaney replaces John Deacon on bass in Queen, and the effect is not so noticeable.

But that wasn’t the case when guitarist Brian May and drummer Roger Taylor selected Bad Company’s Paul Rodgers to tour with the band as a vocalist replacing the late Freddie Mercury.

Rodgers will also play Gretna Fest, but May and Taylor have since said that Rodgers’ macho, blues-oriented vocals weren’t right for their songs.

They’ve found a more appropriate choice in the theatrical, glam-oriented “American Idol” contender Adam Lambert.

The question has a lot to do with tastes as well. It’s easy to be judgmental about bands that are shadows of their former selves when they’re not your bands.

Music journalist Peter Gerstenzang in the Facebook conversation was skeptical of many reconstituted bands, but fine with Westerberg and original bassist Tommy Stinson representing The Replacements on tour this summer.

“If two charismatic members of the original band are still in it, they’re still okay with me,” he wrote.

Why does any of this matter?

If you go to the show and hear the songs you like, isn’t that enough? You got “Free Bird.” You got an epic guitar solo and feel free as a bird now. What’s not to love? Nobody notices that the keyboard player or bass player is playing the original parts.

That’s how most people listen to music. Singles historically outsold albums, and radio and clubs are about songs, not albums.

Album people, on the other hand, love bands and the narratives they create. Lineup changes are meaningful, perhaps signaling consequential results.

When they see Lynyrd Skynyrd with only Rossington remaining, rightly or wrongly they see a band that now is primarily in it for the money.

Skynyrd has continued to record new music, but another contemporary, Billy Joel, decided that his fans only want his old songs and has stopped writing and performing new ones.

The question comes down to investment. People invested in the songs themselves will be forgiving, while those invested in the artists and their stories remain skeptical.

As Dillard professor Nancy Dixon said: “One Temptation is no temptation.”