Secrets of the pop song
It's a hard time to be selling music, as retailer HMV can attest - finding its sales hit by another 14.5% drop this week.
But what are the magic ingredients that songwriters need to make a multi-million-selling hit - be it a ballad, anthem or breakthrough single?
"One of my jobs is to make whoever walks through the door here, walk away with something that is successful to a lot of people," said songwriter, producer and musician Guy Chambers in his north London studio.
Chambers has lifted the lid on his creative process in a new series for BBC Two, Secrets of the Pop Song.
In it, he worked with Canadian star Rufus Wainwright to create a ballad, and with DJ and producer Mark Ronson and up-and-coming singer Tawiah to write a breakthrough single for the new London artist.
He also co-wrote an anthem with band The Noisettes.
So why have his songs had so much airplay in a fiercely competitive market?
"My sound, is comfort food. Warm, not angular, like a roast dinner."
This emotive feeling has helped build his reputation for producing some of pop's biggest-selling songs.
He is well-known for his work co-writing with Robbie Williams - they have sold over 40m albums, and penned Angels, which sold more than 2m copies.
Wainwright wanted to test out the writing relationship, but was initially sceptical about writing the ballad World War III with Chambers, as he said pop was his "soft spot".
"I've written before with people and usually it's a dentistry experience - but with Guy it was a sensibility of 'let's do this for the song'," he said.
The song is being considered for his next album, but it may not get used.
Chambers writes about 80 songs a year - but considers it a good turnout if 30 or so are released.
So where does he start when writing?
Often a sample, riff, hook, lyric, or rhythm begins the process.
"You're always starting from nothing, and that can be quite daunting, especially lyrically.
"The thing about pop songs is you've got to try and use as little words as possible," said Chambers, who has a "four-minute" length rule.
"If you use the word love, you can be in cheese territory, as there's so many titles with the word love.
"Writing about love… it's a challenge, it's much easier writing something that's very conceptual.
"When you have songs where the line repeats and one word is different, the ear likes that, because you're thinking 'where's he going next? What's he going to rhyme it with?'"
Mark Ronson, who has produced artists such as Lily Allen, Kaiser Chiefs and Duran Duran said he found co-writing very intense.
"There's always trepidation because it's a mixture of like a first date, and then also the pressure to actually create something."
Tawiah "a technically brilliant singer" according to Chambers, has been signed to a record label and toured with Ronson's band.
She is set to sing with chart-topper Cee Lo Green, and joined Ronson and Chambers in the studio to create her track Ghost.
She said: "I have a history with Mark... to get in the studio and write with him is really exciting. Guy Chambers is obviously a huge songwriter, so it's an honour."
Tawiah's African roots led Ronson and Chambers to use a Ghanaian guitar style called "high life".
"Too many people think they need to have their own sound right from the beginning," Chambers explained.
"Once you start putting instruments on songs you can then look at it again in a different light. It can change the way you hear it."
His technique is to build the song up, often with a bridge and a chorus "to give a lift".
Tawiah's song was written to "make a big debut", as British songwriter Jesse J's Price Tag did. She has picked up a Brit, the Critics Choice Award and a platinum album.
The Essex singer told the programme: "You know when it's good because you're there (in the studio)... and you go home... and everyone is singing it."
But former Culture Club singer and chart topper Boy George told the programme that pop would never be only about the art of writing a perfect tune: "What makes a 'good' pop song? Airplay!"
Chambers admits it's not always an easy road, but he has made a career out of it.
"The thing about songwriting, is that you never know how it is going to turn out.
"And there's no boss. It's a pretty cool job."
The three-part series Secrets of the Pop Song begins on BBC Two on Saturday 2 July at 2145 BST.