Listen to the story of Stairway to Heaven
In November 1971, we unwrapped the new Led Zeppelin album. Side one, track four, went on to become the band's defining song, an enduring international favourite, and one of the most heard and covered songs ever.
It's not Led Zeppelin's best song. It's not even the best song on the album. But it is a magical thing, a gradually unfolding musical odyssey building from a gentle guitar and recorder duet, to a thrilling, almost symphonic crescendo. Jimmy Page refused to cut it down for a 45rpm release, but radio played it anyway and the song became one of rock's biggest hits.
Page composed the music and the extraordinary guitar parts, to which whole websites and YouTube channels are devoted. Robert Plant's enchanting lyrics are also pored over and analysed for meaning. Because you know sometimes words have two meanings.
Listen to the music of 1991
We're up to 1991 in our continuing exploration of musical change, decade by decade. The first year of the 90s gave us the first Gulf War, the collapse of the Soviet Union, while Australia's national leadership was at war with itself.
The music of 1991 was dominated by dance - the sound of nightclubs ruled the airwaves.
Listen to some of the best live albums of all time
Concert recordings were once a big deal. Live albums captured bands surfing crowd energy, improvising, taking risks. We got to hear what our favourite acts could do as stage performers, free of studio discipline and record company rules.
And not that long ago, top bands were reluctant to make the long journey to Australia, so live albums were often the only way we could experience their concerts.
Some of these records have captured history, like the Bob Marley and Peter Frampton shows that made them global stars.
Listen to the story of rock's first big benefit gig 50 years ago.
It was the first large scale rock music benefit concert. Sunday August 1, 1971. Two shows at Madison Square Garden, New York, in response to an appalling humanitarian crisis in east Pakistan, now Bangladesh.
Indian musician Ravi Shankar was hearing stories of the crisis. He called his friend, George Harrison, asking for help. George phoned some friends, and in just four weeks, put together a stellar line up. Two ex-Beatles, Eric Clapton, Leon Russell, Billy Preston, and Bob Dylan, seen live just once since 1966.
The concerts raised $US250,000. An album and a film continue to raise money - all up, it's more than $20 million. Long before Live Aid, Farm Aid and the others, there was a great show, one of the best live albums ever made, and a great performance movie. The Concert for Bangladesh.
Listen to instrumental hit records
Instrumentals were once common at the top of the pop charts, hitting a peak in the 1950s and 60s. They're rare these days, and it's not clear why they've fallen from favour.
There's a long and honourable tradition of instrumental chart success. Listen to some of the best.
So many great albums were released in 1971. This is the standout. Motown's biggest star stopped doing love songs and wrote about the turmoil he saw around him. America divided on race, on the war in Vietnam. Student protests met with lethal force. Trigger happy policing.
Many of those issues still divide America. New forces fuel disagreement and hatred. What's Going On is fifty years old, but it sounds as if it could have been written last week. It is a deeply soulful prayer for a nation in trouble, full of humanity and compassion. Musically, it's a masterpiece. Motown boss Berry Gordy was nervous when his biggest star said he wanted to make a "protest" album. Later, Gordy said it was Motown's finest moment.
1971: The Year That Music Changed Everything makes the case for a year of great music, landmark albums, and seismic shifts in styles and methods.
Ask 50 people what year they think had the finest music. Answers will vary widely, but you'll be amazed how many says "1971". With good cause. Blue, Sticky Fingers, What's Going On, Aqualung, Cat Stevens, Elton John, ex-Beatle solo releases. The shift from singles to albums was accelerating. Radio playlists got bolder. Record companies took bigger risks. Performers were allowed, encouraged, to experiment.
Rock and pop music has always been dominated by songs in English, recorded by bands from Britain and the US. But there's always been music from other countries, in many languages.
In the 1980s, the industry found a marketing label for those global sounds - "world" music. We could hear and buy music from just about anywhere.
Before that, such music was rarely heard in the West. But every so often, a "foreign" record would break through. Latin dance numbers, African tunes, Indian infused 60s pop.
For many people, their first taste of world music came in 1964, when the dance sequence from the film Zorba the Greek became a global hit. It was written and recorded in one epic night by Mikis Theodorakis to meet a movie deadline. Zorba's Dance was a number one hit all over the world. Mikis Theodorakis was a composer, conductor, and political leader. He died in September.
Listen to the story of Zorba and other early world music hits.
Songs usually stay in one key, one scale or set of notes that are in harmony with each other. The keys of A B C D E F and G, majors and minors, and all the sharps and flats, all have their own distinct flavour and character.
Sometimes, changing to another key during a song adds drama, feeling, magic. It can be a device that adds momentum, or mystery. A good key change can lift an ordinary song into the stratosphere.
AUDIO Listen to some famous rock & pop key changes
Richard is a writer, podcaster, radio and TV broadcaster, an editor, and a lover of music. He tells the stories of how great songs are made, and of the people who make them.