LENOX -- Leonard Slatkin had two instructions to give to his old friend William Bolcom: "The only thing I'm asking is, one, keep it short and, two, do not put ‘Happy Birthday' in."
Slatkin, the American conductor and factotum of American music, turns 70 on Sept. 1. To honor the occasion, the Boston Symphony Orchestra commissioned Bolcom's "Circus Overture" for him. It will lead off the birthday concert the soon-to-be septuagenarian will conduct tonight at Tanglewood.
Slatkin says life is treating him well. He reports that his health is good and the Detroit Symphony, which he has directed since 2008, is moving ahead along with the city. He's planning summers off to write two more books, compose, "slow it down a little bit" and try to enjoy whatever the fruits of his labors may be.
He figures he'll be in Lyons on the big day, rehearsing his other orchestra, the Orchestre National de France. And this will probably be his last Tanglewood visit. After this year he's dropping out of the festival circuit, though he'll still do some guest-conducting during the winter season.
So, farewell to Chicago's Grant Park, Aspen, Tanglewood and Hollywood Bowl. He'll especially miss the Bowl, where his father, Felix, conducted and his son, Daniel, 20, now works as an audio assistant.
By design, tonight's program holds a mirror up to the Slatkin career. In addition to the Bolcom piece, it includes Wayne Barlow's "The Winter's Passed" and Samuel Barber's Violin Concerto, with Gil Shaham as soloist, in an American first half: Elgar's "Enigma Variations" provides an English conclusion.
Slatkin says he conducts many kinds of music but American and English music are probably what he is known best for. The Barlow piece, which will feature BSO principal oboist John Ferillo as soloist, recalls a 20th-century generation of American composers who have been unduly -- outrageously -- forgotten, Slatkin says.
No regrets from this conductor-writer-composer.
"I have a premiere of a piece in October and I have three more on the back burner," he said. "None are commissions. They're all pieces I just want to write and get out of my system. Some are light, some are serious."
A lifetime of conducting, he added, "is a grueling experience. I know that a lot of my colleagues just can't live without being on the podium 24/7." But after a heart attack in 2009 and three months off to recuperate, he began to realize it was time "to clear your head, get rid of stresses, do other projects."
Slatkin reminisced last week from the Aspen Festival, where (can you believe it? he marveled) he has a 50-year history, shared with Bolcom. And the only high he was on out there in Colorado, he said, was the music.
The new books will be sequels to his autobiographical 2012 "Conducting Business," which, he points out, sold 12,000 copies -- a lot for a book on classical music.
In the "Praeludium" to that book, he wrote that being a conductor "requires much more than wielding the baton, score reading and the ability to listen. The conductor also serves as father, mother, psychologist, teacher, referee and many other roles to his hundred-plus orchestra members. He or she operates as a CEO, a visiting team leader, a production supervisor and a social butterfly."
He's working on the two new books simultaneously. Neither has a publication date.
"Unfinished Business" is, as the title suggests, a sequel to "Conducting Business," but now dealing with such topics as artists he has worked with (Arthur Rubinstein and Isaac Stern among them), the after-life of works he has commissioned, and his favorite pieces to conduct (not to be confused, he says, with the frequently asked-about "favorite pieces," he says).
"Conducting Standards," for conductors starting out on their careers, will detail specific technical hurdles in specific works. Unlike other how-to books on conducting, which rely on diagrams, this one will come with a video in which Slatkin demonstrates the options.
A few Slatkin thoughts on the future of classical music:
There are so many talented students that "every time I see them and I work with them, I wonder, what's it going to be like for them 10 years from now?" Will there be jobs?
Economic pressures will force changes in the profession but, as in Detroit, "this is just the way life is now. Economic reality has to be put into some sort of perspective with artistic integrity."
("Each time I conduct," he wonders, "am I worth that amount of money? I don't know.")
It's "fantastic" that audiences now accept contemporary music as part of their regular diet, but the music of the generation of outstanding American composers such as Howard Hanson, Walter Piston and Roger Sessions has disappeared from programs.
"My concern for music in this country is that we are very close to losing our connection with a vital part of our tradition and history," he summed up.
And that's how it looks at 70.