I am at a loss as to how to write "I was listening to the ..." because the translation keeps coming up as "Ich habe mir das Hörbuch Herr der Ringe angehört" however this loses doesn't seem correct because it's saying "I listened to" or "I have listened to" which feels wrong because "I was listening" describes a continuous action during a period in the past while "I listened" gives no such indication and merely states that it happened.
From your comment on the other answer:
What I am confused with though is how to correctly translate verbs that contain the ing endings.
It's okay to be confused. As CallMeCody pointed out in his correct answer, German does not encode the continous aspect into the verb form as English does. If you want to point out that aspect in German, you have to use other hints: a temporal conjuction as als or während, or a temporal adverb as gerade.
What I wanted to add, for your encouragement: you will encounter this problem not only with the continous aspect but with all aspects, modes, voices, tenses German has. The use of verbs in German is very different from English. What makes it hard and confusing is things look alike, but they aren't. Not at all.
- English simple present tense is about the present — while German Präsens tense is about everything but the past.
- English present perfect tense is about actions having a result in the present — while German Perfekt tense is about the past.
- English simple past tense is about the past — while German Präteritum tense is about an reported timeframe, which may be in the past but as well as valid in the future or in some fantasy world. (English does this too, but in German it's the almost exclusive use, apart from some common verbs.)
- English past perfect tense is about actions having a result in the past. — While German Plusquamperfekt has the same function for Präteritum German Perfekt has for Präsens.
- English going-to-future tense is about your future plans — German speakers simply use Präsens tense and time marker words instead.
- English will-future tense is about the future beyond your influence — while German Futur I tense is pretty similar in meaning, German speakers only use it sparsely. They use Präsens and time marker words instead.
This list is just about tenses (though not all of them!) and you already see how different they are used. The use of voices, moods, aspects is even more different.
So it's okay to be confused but don't be frustrated. You don't have to climb that hill in one day. No German ever did. It will come naturally to you as soon as you read/write/speak/listen to more German.
But it is the correct translation.
If you want to stress out that something happened while you were doing something else you use "als" or "während".
"Ich habe mir das Herr der Ringe Hörbuch angehört, als es an der Tür klingelte."
"Ich habe mir das Herr der Ringe Hörbuch angehört, während meine Mutter einkaufen war."
Btw, "das Hörbuch Herr der Ringe" implies that "Herr der Ringe" is the name of the audiobook, just like in english "the audiobook Lord of the Rings".
» … feels wrong because "I was listening" describes a continuous action during a period in the past … «
“I was listening to the Lord of the Rings audiobook …”
You're looking for the temporal adverb "gerade" (often shortened to "grade" or "grad").
Ich hörte grad das Herr der Ringe Hörbuch, da schlug der Blitz ein.
Oder (vielleicht nicht ganz korrekt, aber gängig):
Ich war das Herr der Ringe Audiobuch am hören, da flog ein Vogel durchs Fenster.
Pattern is: Ich bin/war am suchen/arbeiten/schreiben.
Using objects of any case with the verb (like: ich war das Audiobuch am hören) doesn't ring quite correct (see note) to my ears but it is a very useful construction and it is frequently used. So I do use it.
Note: What students (Germans and others) aren't told is that many rules on grammar and pronunciation are too restrictive to account for the huge body of regional idioms, dialects, which is (or was) the true living matter that grammar has been extracted from.