Speaking to told BBC Radio 5live, Richard said: "I said, 'my initial answer is yes but can you check it's not a joke? Is there an ulterior motive?' He got hold of Morrissey's management and he said 'no, Morrissey's a fan and he'd like you to be there.' So I said 'yes please.'
"The chances of me singing for 15,000 people in New York are pretty well nil for me at the moment anyway. So I thought it would be great."
The 73-year-old said he was grateful to Morrissey, but admitted he would struggle to name any of his hits: "I couldn't tell you the titles. I've just googled him to see what kinds of crowds he plays to and what sort of show he did. I'm thinking, okay, it looks like a pop-rock show."
Morrissey's memoir has outsold the latest Bridget Jones novel to top the best seller charts in its first week.
The paperback, called "Autobiography" and published by Penguin Classics, sold just short of 35,000 copies according to sales figures in trade magazine The Bookseller after its release on Thursday.
Helen Fielding's new Bridget Jones novel, Mad About the Boy, sold around 32,000 copies.
Morrissey's book sees the famously private chart star disclose details of how his first relationship with a man came in his 30s and grumble at length about the injustices of a court case about the royalties from his former band The Smiths.
Morrissey has donated £10,000 to an anti-foie gras campaign after Channel 4 compensated the singer for using one of his songs without permission in an advert for a Gordon Ramsay show.
The prominent vegetarian is entirely funding the campaign by People for the Ethical Treatment of Animals (Peta) which opposes the sale of the luxury food at Fortnum & Mason in central London.
Foie gras is the swollen liver of a goose or duck which has been enlarged through the animals being force-fed grain.
The former Smiths singer, who previously released an album titled 'Meat Is Murder', said:
"Ramsay may very well stick his head in his microwave when he hears that the money I received from Channel 4 because one of my songs was used to promote his Christmas show is being donated to Peta to fight foie gras.
"Foie gras is so cruelly produced that he'd be against it if he had an ethical bone in his body."
X Factor host Dermot O'Leary has revealed he bumped into Morrissey as he checked into his honeymoon hotel - and the former Smiths frontman told him his marriage would not last.
O'Leary tied the knot with long-term girlfriend Dee Koppang last month in a ceremony at a church in Kent.
He said the surly singer delivered his gloomy verdict when he spotted him in the courtyard of his hotel in Rome.
In an interview for tonight's Jonathan Ross Show on ITV1, O'Leary said he approached Morrissey, whom he had previously interviewed for his BBC Radio 2 show: "I went over and I said, 'It's lovely to see you', and he said: 'Really? I'm sure you'd say the same thing to Barry Manilow or Gary Barlow'.
"I said, 'No it is. Morrissey, I'm here on my honeymoon', and he said, 'It won't last, these things never do'."