This problem was solved by the creation of iTunes-Affiliate-Links, that lead the listener automatically to the iTunes Store.
Firstly, the user has to join the iTunes-Affiliate Program of Apple (http://www.apple.com/itunes/affiliates). After the registration, you will get the "Partner-ID" and the link to the "iTunes Link Maker"-Web page, where you can generate the specific links (see "Screenshot iTunes Link Maker").
Afterwards, the user can click on the Album, Artist or Song Link and a pop-up opens with the details. The customer can choose between a small and a big button or text only (see "Screenshot Linking"). Finally, the programmer has to insert the resulting HTML-Code into the website.
When a user clicks on the link, iTunes will open and navigate to the correct page. If the user doesn't have iTunes, the link will automatically take the user to an iTunes download page.