Play the 'Escape' level and immediately you have crossed both lava pits high jump up on the left wall and climb it. Continue climbing to the top making sure you do not get hit by any bullets and then go right. You can't turn into the raven because of the machines so go right as far as you can until you find the red skull. Bounce over the final wall and you will see the Boy and Blob behind bars.
To activate a classic 8 Bit soundtrack, you need to push and hold L1, L2, L3, R1, R2, R3, Select and Start all together at the Level Select. You may need to employ some fancy finger work to hold so many buttons at once!