I came out in a rash when I heard that Emma Thompson was to star in Stephen Sondheim’s Sweeney Todd at the Coliseum. Sondheim has that effect on me. And it’s an allergy I bear with pride. I’ve been the victim of a Sondheim evening only once in my life and I emerged feeling as if I’d been shrieked at for three hours by a gorilla with rabies. The show, Sunday in the Park with George, was conceived as an exercise in ‘musical pointillism’ to honour the painter Georges Seurat. Musical pointillism? Come on.

Sondheim has supporters that I admire, like Michael Grandage, and I would put the following questions to these deluded fanatics. Why has Sondheim never had a top 40 hit, apart from ‘Send in the Clowns’ (a mawkishly competent sliver of whimsical self-pity)? Why do today’s star-makers and kiddie-band managers never give Sondheim ‘classics’ to their pop-factory fivesomes? Why did Saturday Night, his first professional outing as composer and wordsmith, have to wait 42 years before receiving its world première? It may be the lyrics. Here’s a number from the show in which a gold-digger laments her entanglement with a pauper.

‘I said the man for me/ Must have a castle./ A man of means he’d be,/ A man of fame./And then I met a man who hadn’t any,/ Without a penny/ To his name./ I had to go and fall/ For so much less than/ What I had planned from all/ The magazines.’

The rhymes are too haphazard to reveal a scheme or pattern. They just crop up at random like serial killers in a rural community. Rap artists use the same method. They improvise their verses while keeping a lookout for verbal replications, and as soon as one appears it gets dumped in the first available slot.

As Sondheim matured he became more pretentious and obscure. Here’s a duet from Follies.

‘What will tomorrow bring? the pundits query/ Will it be cheery? Will it be sad?/Will it be birds in spring or hara-kiri?/ Don’t worry, dearie. Don’t worry lad.’

If you’re filling out a line with ‘dear’ or ‘dearie’, you’re very unwise to draw attention to your ineptitude with rhymes that feel forced. ‘Query’ is an unconvincing alternative to ‘ask’ or ‘wonder’. ‘Hara kiri’ is just bizarre. And ‘dearie’, if we’re honest, is not a word anyone would use except as an insult. The next couplets are even more contrived.

Young Ben: ‘I’ll have our future suit your whim,/ Blue chip preferred.’

Young Phyllis: ‘Putting it in a synonym,/ Perfect’s the word.’

Using a term like ‘synonym’ in a romantic lyric seems a little swottish. But my real objection to the couplet is that it makes virtually no sense.

Sondheim’s fans insist he has merit as a composer. Well, ask a random stranger to hum a Sondheim favourite (excluding those flipping clowns), and I bet you’ll draw a blank. I find absolutely no appeal in his choices of notes and harmonies (I hesitate to say ‘tunes’ in this context for fear of semantic inexactitude). This may be a generational problem. Sondheim came of age during the 1940s when jazz dominated musical taste. To our lot, from the 1960s, jazz seems like a journey without a map to a town that doesn’t exist.

One final question for those fans. Why do your bonces explode when someone says Sondheim’s crap?