O ‘Melveny & Myers is singing a new number — it’s a siren song of sorts, promising its services to fledgling high-tech clients for equity instead of cold, hard cash. The refrain? One fine day, the start-up company might go public and make anyone holding stock richer than rich.

It’s an unusual move for a firm like O’Melveny, which grew to its present girth on a steady diet of fat-cat corporate clients, such as banks, oil barons and defense contractors. But as the next century looms, it’s twilight time for such institutions, at least in Los Angeles.