Possible Clues:

• Instantly memorable
• (Of a tune) instantly appealing and memorable
• Like an earworm
• From what's been heard you won't forget this is caught from yacht at sea
• Like songs that get stuck in your head
• Attention-getting
• Like a memorable tune
• Easy to remember (tune)
• Easily remembered feline found with small child at day's end
• (Of tune) memorable