It is staple fare in the mainstream. It is never far from concert programmes. Every symphony orchestra in the world has Brahms One under its belt. Its devotees are addicted to every turn, flavour and colour of the music, from its dark, treading introduction, the seething drama of the main section which follows that intro, the gorgeous slow movement with its intertwining of French horn and first violin melodies; the sophistication and grace of its third movement, which has a fiery turn; and the great theme of the finale, which rolls out like a carpet of velvet sound after an long approach from a runway that features mysterious, tension-building music. Once the music is in your blood, it is unforgettable and addictive.

But, and it is a big but, some people have a problem with Brahms in general and this piece in particular. Nobody had a bigger problem with it than Brahms himself. More of that in a moment. There are people, music lovers, who just find the symphony too dense, too weighty, thick-textured and heavyweight; it was once described as an over-upholstered piece of furniture.

Peter Oundjian, who will be the Royal Scottish National Orchestra’s music director from 2012, and who is himself a fine conductor of Brahms, recalls distinctly being taken to hear one of Brahms’s four symphonies as a youngster. The conductor was the great German, Otto Klemperer. “I was very young and I was very bored. There was not a lot of electricity flying around.” He reckons that it was the way that Brahms used to be played. “I think we went through a period where it was very formalised and elitist; Brahms can be tough. And it’s up to us to figure out what the actual furniture is, and how to upholster it.”

Composer Stuart MacRae has had to write a companion piece, a sort of homage, to one of the symphonies. And he understands the problem. “Brahms can take a while; but once you get it, you REALLY get it.”

Not everyone has that experience: the British composer Edward Gregson was introduced to Brahms One while at school, and it blew him away. “The visceral impact of that raw power and passion was overwhelming.” What took a little longer to grasp, he said, was the “intellectual craft”. And it is massively intellectual music, though Brahms was long dead before the world began fully to appreciate the significance and influence of his near-unique craftsmanship.

Brahms himself worried that people were not going to get his music, that it would be impenetrable. What were the issues? What was the problem that Brahms had with the symphony? And clearly, there was one. It took him almost 21 years to get it done. It was started, stopped, started again, set aside, picked up and laid down on numerous occasions.

When it was well under way, he was approached by conductors interested in performing it. He had started it possibly as early as 1855, when he was in his early twenties. But even by 1870 he was, in the words of one analyst, “far from confident about the outcome”. Even when it was eventually finished, in 1876, just before the premiere Brahms felt compelled, as one historian has put it, “to attack it and make cuts to the two inner movements”.

The problem he had was immense. It can be summed up in one word: Beethoven. Beethoven had revolutionised and exploded the form of the symphony. He had done the lot in his nine masterpieces. In symphony after symphony, he had smashed through the entire concept and construct of symphonic form. And Brahms knew it.

How to follow that and extend the form was the issue. And we know from his own words the pressure Brahms felt, and the awesome responsibility he assumed in continuing with the symphony as a species after Beethoven, who had died in 1827.

“You don’t have any idea,” Brahms wrote to a conductor, “how it feels if one always hears a giant marching behind one. I shall never compose a symphony.” On another occasion, he wrote this: “Oh God, if one dares to write symphonies after Beethoven, they must look very different.”

And there were other pressures too, of which Brahms was certainly aware. Music in Germany was changing. There was a new movement. It was the modernist movement, the avant-garde, spearheaded by Richard Wagner and Franz Liszt. These were the futurists. Wagner declared the symphony as a species dead, and that the new way forward was his way. It was an entire movement, and, by their philosophy and practice, Brahms was something of an anachronism.

Brahms knew all this but, one polemical encounter with the experimentalists apart, doggedly stuck to his determined path. The enormous gestation period of the First Symphony has sparked many theories, of which a favourite is that, as he picked away at the First Symphony, developing it, lifting and laying it, grappling with the issues it threw up, Brahms wrote other orchestral works to refine and cultivate his orchestral technique while he approached a solution to the Beethoven problem.

There is truth in this of course. His experience and expertise was accruing every time he put pen to paper. But somewhere in this equation there is a very basic observation to be made. It’s not a new one, but it’s one that is not always given its appropriate significance. Bluntly, Brahms had a block. And it was the Beethoven block. Read his words, above. It’s all there.

Moreover, look at the list of works he produced during the period when he couldn’t get that symphony out of him. In 1857 he wrote the First Serenade. In 1858 he wrote the Second Serenade. Between 1854 and 1888 he produced the awesome First Piano Concerto, one of the greatest of the century. In 1873 he wrote the amazing Variations on a Theme of Haydn, one of the most popular pieces in the repertoire. And between 1857 and 1868 he wrote the German Requiem, the greatest choral Requiem of the century, apart from Verdi’s.

Look at that list. This is not a composer who’s testing himself, or practising his art and his craft. He’s not an apprentice. These are masterworks, with fantastic creativity and superbly confident and effective orchestration. Brahms didn’t suffer from a general creative block. It was only that damned symphony and the shadow of Beethoven.

And when he finally did get the First Symphony out of his head, on to paper and premiered in 1876, something remarkable happened. Guess what? It was cathartic. The First Symphony had taken 21 years. Getting it out of his system turned a key in the lock and released his powers.

He began his Second Symphony almost immediately, and he finished it in less than two months. Five years later he started the Third Symphony and it was done in less than four months. He wrote the Fourth and final Symphony within a year.

The First Symphony is a great symphony. In some ways it is a tough nut to crack. This is fanciful and deeply personal, but I always imagine, when listening to it, that you can actually sense Brahms’s internal struggle, especially in the opening movement, and on that lengthy runway into the finale, where, when the great, long, typically- Brahmsian theme rolls out, you can sense that this is the moment of catharsis.

There are hundreds of recordings, and I have many favourites. One that I always return to is Marin Alsop’s with the London Philharmonic Orchestra on the super-budget Naxos label. There’s nothing tricksy about it. It’s honest: it’s about the music, not showing off an orchestra or a conductor’s interpretation. She gives it plenty of space, depth and a very good breadth. It’s very dramatic and, at appropriate moments, extremely beautiful.

And, if you’re new to it, how should you listen? The world is full of listening guides, programme notes, books, essays, and so on. My tip? If you don’t know it, stick it on while you’re doing other things. Let it be your background. (I do that all the time with tough, unfamiliar music.) Keep doing it. Just let it play.

One day something will stick and get a wee hook into you. It might be a tune, or a rhythm, or a chord, or a particular instrumental effect. That will grow in all directions through the symphony. The jigsaw will begin to assemble. And once it’s got you, it will never let you go; it’s for life.