Verified answer

"How come I can listen to some tracks in full length a few times, and then they play only as 30 second previews?" - "If this happens to you, you probably live in the US, UK, or Germany. In these countries, we currently offer a service called Free On-Demand which allows you to listen to specific tracks up to 3 times on demand, in full length and for free.

Afterwards, these tracks will be played as 30 second previews for you. This doesn’t affect the radio – in radio stations, all tracks will always be played in full length, even if you’ve used up your 3 plays limit for Free On-Demand."

" How can I listen to a specific track?" - "You can listen to any track where you can see a play button (white triangle in black circle) next to its name, or selecting it from the player on the site if it’s listed there.

By default, we can only allow for you to listen to a 30 second preview of a track. Should the rights holder allow for there to be a full length preview available, you'll find the words “full track” next to the track name.

If you live in the US, the UK or Germany you can also listen to many tracks in full length up to 3 times for free by using our Free On-Demand service."

properly some i detect greater suited then others its not that they dont want you to purchase. its probable purely a working laptop or laptop randomly choosing out the preview so specially circumstances it receives a great part of a song and different circumstances it doesnt.