My son is called a note tracker, which means he listens to the song and 'transcribes' the song for the programmers to incorporate into the product. It's not just saying "an
Am is played there" but also if a riff has bends, tapping, harmonics etc. FWIW my son has near pitch perfect hearing. At fifteen he told me a commercial bass sample I had was out of tune. We plugged the output of the sampler (Ensoniq EPS) into a tuner. He was right, the sample was a half needle width off dead center.