Steve Jobs has called for them to allow their music to be sold DRM free.
Only EMI responded, and to this day, only their catalog is available on iTunes without restriction.
From Steve Jobs' "Thoughts on Music"
February 6, 2007
Since Apple does not own or control any music itself, it must license the rights to distribute music from others, primarily the “big four” music companies: Universal, Sony BMG, Warner and EMI. These four companies control the distribution of over 70% of the world’s music. When Apple approached these companies to license their music to distribute legally over the Internet, they were extremely cautious and required Apple to protect their music from being illegally copied. The solution was to create a DRM system, which envelopes each song purchased from the iTunes store in special and secret software so that it cannot be played on unauthorized devices.
Apple was able to negotiate landmark usage rights at the time, which include allowing users to play their DRM protected music on up to 5 computers and on an unlimited number of iPods. Obtaining such rights from the music companies was unprecedented at the time, and even today is unmatched by most other digital music services. However, a key provision of our agreements with the music companies is that if our DRM system is compromised and their music becomes playable on unauthorized devices, we have only a small number of weeks to fix the problem or they can withdraw their entire music catalog from our iTunes store.
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The...alternative is to abolish DRMs entirely. Imagine a world where every online store sells DRM-free music encoded in open licensable formats. In such a world, any player can play music purchased from any store, and any store can sell music which is playable on all players. This is clearly the best alternative for consumers, and Apple would embrace it in a heartbeat. If the big four music companies would license Apple their music without the requirement that it be protected with a DRM, we would switch to selling only DRM-free music on our iTunes store. Every iPod ever made will play this DRM-free music.
Why would the big four music companies agree to let Apple and others distribute their music without using DRM systems to protect it? The simplest answer is because DRMs haven’t worked, and may never work, to halt music piracy. Though the big four music companies require that all their music sold online be protected with DRMs, these same music companies continue to sell billions of CDs a year which contain completely unprotected music. That’s right! No DRM system was ever developed for the CD, so all the music distributed on CDs can be easily uploaded to the Internet, then (illegally) downloaded and played on any computer or player.
In 2006, under 2 billion DRM-protected songs were sold worldwide by online stores, while over 20 billion songs were sold completely DRM-free and unprotected on CDs by the music companies themselves. The music companies sell the vast majority of their music DRM-free, and show no signs of changing this behavior, since the overwhelming majority of their revenues depend on selling CDs which must play in CD players that support no DRM system.
So if the music companies are selling over 90 percent of their music DRM-free, what benefits do they get from selling the remaining small percentage of their music encumbered with a DRM system? There appear to be none. If anything, the technical expertise and overhead required to create, operate and update a DRM system has limited the number of participants selling DRM protected music. If such requirements were removed, the music industry might experience an influx of new companies willing to invest in innovative new stores and players. This can only be seen as a positive by the music companies.