According to a release "four Piano media partners will add new and exclusive content to Piano including advance access to premium articles and TV series, press photo galleries and a new ad-free website", as of today's latest increase in content. The Slovakian paywall currently includes 11 publishers in total.
"Piano's media partners are feeling progressively more comfortable with Piano's system as they increase available exclusive content within the subscription system for a third time," the release adds. The last increase in content was in February.
Piano says its partners "have seen a good response from Slovakia's 2 million plus internet users and are pleased with the additional revenue returned", although no specific revenue or subscriber statistics could be shared.
Piano Media's country manager for Slovakia, Rado Bat'o, told Journalism.co.uk that the "number of subscribers is increasing", but hopes the introduction of new content for subscribers will make this "more speedy".
"We can get really more subscribers with different kinds of content", he added.
He said that "in a month, or two months", they will be able to see how the additional content has performed.
Bat'o told Journalism.co.uk the addition of more content will make the subscriber offering " more colourful".
"What we are trying to do is increase reach of the content to maybe some other demographics, or other sorts of readers, who may be not so interested in, for example, political commentaries and things like that, but maybe more of the other stuff."
He said the decision on what content to include in the paywall and which should remain free is "always an agreement between us and publishers".
"We are not the owners of the content, we are just providing the services and the whole system but the content belongs to publishers so it's a question of negotiation, it's a question of their strategy, of their future plans with paid content, so it always depends on the negotiations between us and the publishers".
The changes only apply in Slovakia, he added, and not in Poland and Slovenia which both launched national paywalls with Piano Media this year.
At the time of the launch of the Polish paywall, participating publishers were said to have placed between 10 and 15 per cent of its content behind the wall, compared to around five per cent at the launch of the Slovakian paywall.
Slovakia "was the first country who ran this system", Bat'o added, "so it was like after more than a year we just decided it's time to increase the offer to subscribers".
"Of course there is still not a magical solution to these payment systems ... so we think a good strategy is to do it instead incrementally.
"Now people in Slovakia are used to the fact that there is a national paywall system, they have to pay for some sort of content. Our strategy is to include more and more content so the offer will be better."
The Piano paywall in Slovakia costs €3.90 per month or €39 for a year's access.
In its release, Piano Media adds that it is "in negotiations with publishers in 11 European countries and has plans to launch in one more market by the end of 2012".