WHATEVER TROUBLES Mayor Barry has been experiencing with top aides lately, in his choice of Richard G. Siegel as acting budget director, he has recruited an expert in the finances of this city. Given the resignation of deputy mayor for finance Alphonse G. Hill -- whose duties included supervising the city's budget -- Mr. Siegel's knowledge is all the more important. It is not "new talent," because Mr. Siegel has been budget director for the D.C. Council and a top aide to Council Chairman David A. Clarke and, before that, worked as a budget and financial official for the executive branch. Thus he should, as one administration official said, "hit the ground running."

There were some political grumblings in the council to the effect that Mayor Barry chose Mr. Siegel to upstage Chairman Clarke, who himself has been considering -- though not aloud -- challenging Mr. Barry. Naturally, aides to Mr. Barry said no, politics had nothing to do with it. Of course not, and bring on the tooth fairy riding a unicorn. But forget those political points scored -- it's a sound selection. Besides, Mr. Siegel was known to have been seeking a new job for months. And up to now, he has stuck to financial numbers, not political ones.

City hall's financial management system has been refined considerably in the past few years, and Mr. Siegel's knowledge of it enabled the council to monitor the computerized functions and improve its reviews of the mayor's annual budget proposals. That has strengthened the legislative branch considerably -- and in turn, the ability of both branches of the local government to monitor its revenues and spending in a more sophisticated and efficient manner.