The brainchild of former chief conductor, Hugh Wolff, the idea was to pair the orchestra with leading exponents -- both conductors and soloists -- of the early music, period instrument or historically informed performance movement and explore repertoire that is nowadays no longer associated which a large modern symphony orchestra.
It was Wolff, during his nine-year tenure in Frankfurt from 1997 until 2006, who first introduced valveless horns and trumpets and kettle drums for performances of the symphonies of Haydn and Beethoven, changed the seating order of the strings and minimized their use of vibrato.
In that sense, neither the orchestra nor the audience was treading on wholly unfamiliar ground when the Barock+ series was launched in November 2004.
But what was exciting was the prospect of the orchestra tackling -- on modern instruments and at a modern concert pitch of A = 440 Hz -- works that seem to have dropped out of the repertoire of a modern symphony orchestra and become the sole preserve of period instrument ensembles.
The very first concert on November 26, 2004, featured countertenor Andreas Scholl in arias by Händel sandwiched between Haydn's 89th and 91st symphonies.
On December 17 of the same year, the irrepressible Emmanuelle Haïm gave her German debut conducting Händel's rarely performed oratorio La Resurrezione while Christopher Hogwood conducted works by Haydn, Mozart and Schnittke on February 25th, 2005.
Wait a minute. Run that by me again.
Ah yes. Alfred Schnittke (1934-1998) made use of baroque forms in his works.
I get it. He composed a number of Concerti Grossi.
The series, so it seemed, would explore the influences of the baroque on later composers and their music. Hence the "+" added to the series' title.
Many of the hr-Sinfonieorchester's regular subscribers have never seemed inordinately fond of baroque music anyway.
Maybe Wolff saw it as way of making it more palatable for an audience that generally only wants to hear the core classical and romantic repertoires.
Given such prejudices, I sense it came as something of a surprise to all concerned that Barock+ proved such a runaway success.
The Sendesaal -- with its excellent acoustics and much more intimate atmosphere than the Alte Oper where the hr-Sinfonieorchester gives its regular subscriptions series -- was regularly sold out. And over the years, the series was lengthened from three to four concerts and extended from one to two nights.
Nevertheless, for real baroque aficionados, the title of the series has always appeared rather tenuous, a bit of a "Mogelpackung" to use the German term.
The number of baroque works actually performed has never been particularly extensive, with the focus largely on the early classical.
In fact, I've heard a number of subscribers quip that a more appropriate name would be "Klassik minus" rather than Barock+.
Of course, that is not do dismiss the high quality of the performances per se, even of the non-baroque works.
Last season, Jean-Christophe Spinosi, after conducting the overtures to Händel's Serse and Rameau's Platée before the interval, took everyone by surprise and gave an eye-opening interpretation of Ravel's La Valse and Boléro in the second half. Not repertoire you would normally associate with the man who has almost single-handedly pioneered the renaissance of interest in Vivaldi's operas.
I don't mean to be curmudgeonly.After all, Emmanuelle Haïm returned last November to conduct an exquisite programme of Lully, Purcell and Rameau.
But the next concert in this season's series very much demonstrates my point.
OK. There will be a baroque work: Bach's B-minor Suite performed with the orchestra's phenomenal solo flautist, Sebastian Wittiber.
But that's where the "Barock" stops.
Dazzling a player though Sebastian is, I can't imagine he'll be playing on a baroque flute or even a wooden Böhm one.
Then Fazıl Say will perform Mozart's A-major Concerto KV 414.
And most puzzling of all, Paavo Järvi will conduct the hr-Sinfonieorchester in Franz Schmidt's 2nd Symphony after the interval.
I don' think it's uncharitable to say that the choice of works seems, ahem, a little arbitrary.
[Järvi, it should be pointed out, has never previously conducted a Barock+ concert during his entire time in Frankfurt, which comes to an end this season.
And while he has taken on board some historically informed practices for his critically acclaimed Beethoven and Schumann cycles, Järvi is not a conductor you'd normally turn to for early classical or baroque repertoire.]
In fact, the only reason that I can see that Schmidt (1874-1939) -- a late Romantic composer barely known outside his home country of Austria -- is being performed is that Järvi will be conducting his 3rd Symphony next season and is embarking on a cycle of all four symphonies.
That's all well and good. But what has it got to do with the baroque?
Perhaps the programme notes will enlighten me and explain the dramaturgy behind it all.
Watch this space for a write-up of the concerts on Friday, March 8 and Saturday, March 9.