Despite what many are claiming, this year marks Jethro Tull’s 49th anniversary, not its 50th anniversary.

“I come across that all the time. People just seem to want to jump the gun,” says Ian Anderson, lead vocalist, flautist, acoustic guitarist, and founding member of Jethro Tull.

“But honestly, even if it was, this has been just another tour. It’s been just another tour since the beginning. I’m not an anniversary guy. It’s just not on my mind. I don’t think that way.”

Jethro Tull by Ian Anderson is touring the United States in 2017, playing some of its biggest hits, including “Locomotive Breath,” “Living In The Past,” “Bungle In The Jungle” and “Aqualung,” with a Musikfest concert at 7:30 p.m. Aug. 13, Sands Steel Stage at PNC Plaza, SteelStacks, Bethlehem.

Jethro Tull, which released its first album, “This Was,” in 1968, achieved commercial success in 1969 with the folk-tinged blues album, “Stand Up,” which reached No. 1 in the United Kingdom.

Subsequent albums include “Aqualung” (1971), “Thick as a Brick” (1972), “A Passion Play” (1973), “War Child” (1974), and “Minstrel In The Gallery” (1975).

Tull, as fans call the group, has sold an estimated 60 million albums worldwide, with 11 gold and five platinum albums. Rolling Stone magazine called Jethro Tull “one of the most commercially successful and eccentric progressive rock bands.”

Just after the 2017 tour started, the band released “Jethro Tull - The String Quartets,” an album of its most popular songs re-imagined as classical compositions performed with the Carducci String Quartet.

“It was one of those little side projects I had in mind for a couple of years,” Anderson says in a phone interview. “We started to put together a few thoughts in hotel lobbies and odd little meetings, sketching out the ideas of possible songs, and then in September I started to work with the Carducci Quartet, who I happened to have met a few weeks prior.”

Anderson, who turns 70 on Aug. 10, has always been drawn to the sound of string quartets, feeling they have a certain spiritual charm. In this vein, the album was recorded in the Worcester Cathedral, Worcester, England, and St. Kenelm’s Church, Witney, England.

“They provided a spiritual atmosphere that I felt the music would benefit from. Not acoustically. It was really just the spiritual element that I wanted to bring into it.”

Anderson was born in Dunfermline, Scotland, grew up in Edinburgh, and moved to Blackpool, England. The band is named for Jethro Tull, an 18th-century agriculturist.

While being a wildly successful instrumentalist capable of playing music in many forms, Anderson (keyboards, bass guitar, bouzouki, balalaika, saxophone, harmonica, and whistles) has always wanted to play the violin.

“I’ve always had a hankering to learn the violin, but it’s a fiendish instrument to play. You can’t just pick it up and quickly arrive at a level of proficiency. It takes years of practice, of which I haven’t had the time or conviction.”

With Anderson having been in the music business for as long as he has, one must wonder what motivates him to continue to create and be such an active member of the community. To him, though, the answer seems almost matter-of-fact.

“It’s that you have a great sense of this being what you do as a creator and as a person. And in terms of touring, it’s romantic. It gets in the blood.

“There will be a time when I’m not enjoying the idea of doing it. Some day, it will lose the appeal. But as long as I can physically and mentally be able to do it, I’ll keep doing it.”

Turning attention back to the Musikfest concert, Anderson hopes that listeners find his music evocative of imagery in ways that he sees his music.

“I want people to try and hear the music and paint their own pictures as to what it’s about. That’s where I start with most visual ideas. It’s a pictorial focus. I think in visual terms, so it’s logical to me that people listening will just close their eyes and create their own pictorial ideas of what it means. Not necessarily the same as mine, but their own interpretations.”

For many, Musikfest will provide a once-in-a-lifetime opportunity to see, with eyes wide-shut or open, one of the most prolific bands still in the music scene live, playing its best works.

Information: musikfest.org; 610-332-1300