The audio player interface allows playing from a streaming service - e.g. a radio station
This is a continuous stream that could run for many hours - but the skill is only given the opportunity to provide song information at the start.
It could respond to user requests - such as "What song is this?" (which is OK) but, primarily for devices with screens, it would be useful for the skill to be able to provide title/subtitle/graphics as the songs change within the continuous stream.

This could be done by having the Skill start the audio stream with a duration parameter which would result in a callback when it is about to be reached - similar to the PlaybackNearlyFinished request.
The Skill could then send new metadata (potentially with an offset to say display in X seconds) and with a new duration parameter.

An alternative approach that could work without any skill being developed at all ...
If the player automatically took the metadata from an ICY stream (as provided by Shoutcast / Icecast servers) then it would be a good alternative - especially if the skill to parse a regex that should be used to parse the ICY title - with a default that would handle "artist name - song title" which is what many internet radio stations use (and StreamURL for the image).
For example ...
Playing http://www.dandelionradio.com/DandelionRadio.pls.

Name : Dandelion Radio
Genre : Alternative
Website: http://www.dandelionradio.com
Public : yes
Bitrate: 128kbit/s
ICY Info: StreamTitle='Rocker: D. A. Stern - Isn't It Obvious?';StreamUrl='http://www.dandelionradio.com/images/drlogosq-black.jpg';