I have half a dozen earworms, Helen. I can switch freely from one to another, but I can't not have one at all! The piano concertos are a wonderful body of work and choosing favourites is very subjective. The one in G, K453 (forgotten what number it is), no 23 in A and the last one, no 27 in B flat, are all sublime. His two minor-key ones, no 20 in D minor K466 and the C minor one, no 24, K 491, are full of smoky drama and, at times, pathos. My very favourite is the one in C, K 467, of Elvira Madigan fame. It's the perfect work of art just as The Magic Flute is perfect. Go on, give them a whirl! If you want really nice performances, any by Murray Perahia will get you there. Or Mitsuko Uchida. Many more but I don't keep up!