Why does 듣다 change to 들었어요? Can someone help me, please?
I don't get the verb 듣다.

Why does the ㄷ change into a ㄹ in the form 들었어요?
Only I heard = 저만 들었어요.

Is it because it is easier to pronounce?
Can someone help me, please?

Question

Why does 듣다 change to 들었어요? Can someone help me, please?
I don't get the verb 듣다.

Why does the ㄷ change into a ㄹ in the form 들었어요? 
Only I heard = 저만 들었어요.

Is it because it is easier to pronounce?
Can someone help me, please?

Answer

I guess you are right. '듣' is cannot be followed by some special words like "음악 (듣었다->들었다) (듣어봐->들어봐) (듣을거야->들을거야)".
There is something in common. You can find it

듣+었   듣+어  듣+을  -->  if 듣 is followed by sort of  'ㅇ' words(The words have 'ㅇ' = vowel sounds),  ㄷ change into ㄹ