Yo la música cuando el teléfono

eschuché

eschuchéó



ó

 escuchaba.....sonó

Yo escuchaba la música cuando el teléfono sonó.

I listened to music when the phone rang.

Explanation: "escuchaba" is conjugated in the imperfect, as something in process without defining if it was completed and the verb "sonó" is conjugated in the preterite as a completed action that interrupts the action that was in process.