"...a living tradition that remains at the heart and root of just about every musical now playing in the West End or on Broadway"
He probably doesn't have Mamma Mia in mind but, even so, "heart and root" is a big claim.
"It is built on Gilbert's genius for light rhymed verse and Sullivan's genius for melody, which combine in a fusion of text and music that has rarely been equalled, let alone surpassed"
I'd quibble with that one. G&S certainly had their influence on musicals, particularly G. Ira Gershwin, for one, was a Gilbert fan. You can hear it in his lyric to this comedy number from Of Thee I Sing:
"She's the illegitimate daughter of an illegitimate son
Of an illegitimate nephew of Napoleon...
She's contemplating suicide
Because that man, he threw aside
A lady with the blue blood of Napoleon "
Gershwin even goes for the ol' operetta trick of inverting the sentence order to make the rhyme ("Because that man, he threw aside").
But these Gilbert-esque ditties are not what Ira Gershwin is famous for. It's this:
"I got rhythm
I got music
I got my man
Who could ask for anything more?"
This is most un-Gilbert-esque and provides a very different "fusion of text and music". It's not just the casual slang ("I got") that distinguishes it. It's the irregularity of the meter in the final line that's the real tell-tale. It doesn't read well. It's not very satisfying as spoken verse. The words only work, only make sense, only really come alive when they're set to music. You couldn't easily transplant these words onto another tune or vice versa. This is the difference. As Mr. Christiansen rightly points out, Gilbert wrote "light rhymed verse". But Gershwin wrote lyrics.
I suspect the real influence of G&S on musicals is less formal. Beyond those early Broadway lyricists and into the era of the integrated musical, their light grows dimmer. You can't really hear any of their style or structure in the musicals of Rodgers and Hammerstein (R&H), let alone Stephen Sondheim (S&S) or Andrew Lloyd Webber (AL&W).
But there's no doubt that they set a standard. They demonstrated that musical theatre could be of smart, sophisticated, tuneful and funny. They provided a link to the Old World operetta and an alternative to the vaudevillian model of musical comedy. Maybe not the "root" of every musical then, but certainly the heart.
