If you want to retrieve the “score” column from solr (which shows relevancy), you need to add a field list parameter to the URL:
fl=score
If you only add this, you won’t get any of your columns, so you want to add *, to get the rest of them:
fl=score,*
Alternately, you can list the columns you want manually, which will likely significantly reduce the payload size of your download:
fl=score,score,id,word_count,audio_length