Symphony Scores Tonight kicks off two and a half weeks of parties in the name of the Houston Symphony Ima Hogg National Young Artist Competition. Notable Houstonians will open up their homes, their boats and their businesses for shindigs of varying magnitudes, hosting parties and dinners with an international flavor. Tonight the theme is "Music and the Maestro," and ticket holders will begin the adventure with cocktails at the Four Leaf Towers home of Houston Symphony conductor Christoph Eschenbach, then move about the building for salads and entrees, concluding the evening with dessert in the company of hosts Ermy and Gordon Bonfield. Proceeds provide young artists the opportunity for a solo instrumental performance with the Houston Symphony. Tickets for the various gatherings range from $25 to $750; a mere $500 gains you admittance to "Music and the Maestro." For more information, call 238-1435.