All Students preparing for Grade exams are recommended to use the Hofnotes on-line training pages to practise for the aural tests.
At higher grades you must be able to discuss with the examiner musical features such as texture, form, style, and period of a piece of music. My own web pages to help with these parts of the test at Grade 5+ and at GCSE are available here!
JS Bach's Art of Fugue
The highpoint of the contrapuntal texture, fugue is a form in its own right.
A short subject is announced by each part in imitation, then used again and again, with various modifications.
the Fuga a 2 claviers, the last movement of JS Bach's Art of Fugue.
Notice that the subject is "answered" at a different pitch. Can you identify the interval between subject and answer?
While the answer is heard, what do you notice about what the first voice did?