You can interact with automatically generated topic channels (those starting with HC ) by subscribing to them, like any other channel.
If you just want to get a list of videos related to the channel, you need to use the future v3 API and you can search based on the main theme. You can get topic identifiers (s) related to this channel using channels.list(id=CHANNEL_ID) :
https://developers.google.com/apis-explorer/#p/youtube/v3/youtube.channels.list?part=topicDetails&id=HC9BkB0bbvR-4
(v3 is not published publicly now, so you need to use the Google API Explorer.)
This returns the theme identifier (Freebase) /m/025g__ , which can then be used for search.list(topicId=TOPIC_ID, q=BLAH, type=video)
https://developers.google.com/apis-explorer/#p/youtube/v3/youtube.search.list?part=snippet&type=video&q=j+pop&topicId=%252Fm%252F025g__
Unfortunately, you cannot perform a search that simply indicates topicId= without q= right now in v3, but this error, which I hope will be fixed soon. So you need to specify something meaningful for the q= parameter, and I just use j pop .
Jeff posnick
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