When Rupert Murdoch tried to buy the part of BSkyB he didn't own, which would give him 40% ownership of all British commercial TV, there was political and media outrage, yet we've seen no such reaction to the news of Universal's swoop for EMI, despite the fact that the deal will give it more than 40% of the recorded music market – creating what Warner Music's exiting chairman calls "a super-major".

Warner Music has tried to buy EMI more than once in the past decade, but was prevented from doing so by regulators. So why would they approve a merger between EMI and the much bigger label Universal? Because of piracy, apparently. Universal claims that due to the decline in recorded music revenue EMI needs investment – and the merger will provide it. But will it?

Universal says it would like to keep EMI as a freestanding company, and that not much will change except that its head will have to answer to Universal boss Lucian Grainge. But is that what will happen in the long run? Remember A&M? Bought by PolyGram. Remember PolyGram? It was bought by Universal's previous parent company, Seagram, in the late 90s, creating the company that became Universal. Remember BMG Records? Bought by Sony, which initially changed name to SonyBMG (as it was a "joint venture") but later dropped the BMG part when Bertelsmann sold its half share. The list of casualties goes on.

In 2007, Universal stated: "Following its recent acquisition of the V2 Music Group from Morgan Stanley, Universal Music has committed to continuing the V2 label, with its own roster of unique artists, and to continuing Cooperative Music, representing independent labels in international markets. This commitment is international in scope, and will give new resources and new energy to the V2 identity, its heritage and its artists."

A week later, when 90% of V2's staff faced redundancy, its managing director, David Steele, told Music Week: "Some of us hoped they would try to re-energise the whole label and some feared they would just asset strip it. Obviously it appears to be the latter. But that's the way the whole industry is going. Labels get bought and they lose their identity, and V2 is another one that's gone."

Universal has plenty of incredibly passionate and knowledgeable people working for it who clearly care about the artists they work with, as do all music groups. As Michel Lambot, founder of music licensing and distribution company PIAS, said recently: "I don't hate major labels – I just wish there were more of them." Even Tony Wadsworth, former head of EMI and now chairman of the British Phonographic Industry, said: "It's not healthy to have a few large companies having all the hits."

Universal argues market share doesn't equal market control, and points to Adele's global success as proof that major label dominance doesn't hamper market access for indies. Research service Music & Copyright is running a poll on this and, at the moment of writing, the overwhelming response is that it does. Adele is a phenomenon – and would be even if she was signed to a major. In the UK she is signed to XL, part of the Beggars Group, but when it came to the US the label decided to use the marketing might of Columbia (part of Sony), despite having its own US office.

Martin Mills, head of Beggars, explains why market share makes a difference: "Q Magazine has 12 covers a year. If Universal has 50% of the market, it would get six covers a year. But it may use the leverage of its big artists to get its not-so-big artists on the cover, and push its number of covers up to seven or eight, That means that all the other labels have four to five covers to split between them."

The same goes for TV shows such as Jonathan Ross and Alan Carr. All labels do this, which means the more big artists you have, the higher the likelihood that you can get one of your new artists on a show, and so increase your market share even more.

Another concern is the power Universal would sway in negotiations with digital music services. Last year Universal sought to block French streaming site Deezer from using its catalogue after it refused to comply with new restrictions imposed by the label, which would limit its free offer to listening to five consecutive songs.

The Paris high court, however, sided with Deezer, concluding: "The refusal to supply the catalogue, following the refusal to accept the conditions of Universal, which differed from those contained in previous contracts and in contradiction with the commitments made during the agreement of January 2011, constitutes in itself an abuse of a dominant position [...]

"It cannot be contested that Universal's catalogue is most important from both a quantitative and a qualitative perspective, as it contains 50% of the Top 100 titles. It can therefore be considered as an essential and thus indispensable element for the size and coverage of the platform."

Put it this way – as we've witnessed, a streaming service can continue without Adele's inclusion in the repertoire. It would even survive without all of XL's catalogue, but not without Universal/EMI's.

Universal has around 40% of the entire French market. A merger with EMI would push it over the 50% threshold. If the merger is approved, Universal will be able to command even larger advance payments and pretty much dictate the terms of any agreement. While Sony will still have some negotiating power, Warner's will diminish considerably (which, God forbid, could eventually lead to there being just two majors), and the independents will be fighting over the crumbs, making it even harder for them to invest in new artists.

Universal is fighting hard for the deal to go through – the stakes are high for the label, too. It has guaranteed Citigroup, the current owner, the £1.2bn price. If the deal isn't approved Universal will have to sell EMI from a position of extraordinary weakness, which could get the orchestrators of the deal in trouble with its parent company, the international media conglomerate Vivendi.

But there's something even more important at stake here: musical diversity. Ask yourselves: would it be better protected by a healthy competitive market for numerous players or by the near duopoly of two corporations?