FAQ for
You've Got Mail (1998) More at IMDbPro »

It's an Austrian folk song known as "The Instrument Song" or "The Orchestra Song". Here are typical verses, which vary a bit from what is sung in "You've Got Mail":

The violins ringing like lovely singing. The violins ringing like lovely song.

The clarinet, the clarinet, goes doodle doodle doodle doodle dat. The clarinet, the clarinet, goes doodle doodle doodle dat.

The trumpet is braying, Ta ta ta ta ta ta ta ta ta ta ta ta ta ta ta ta ta.

The horn, the horn, awakes me at morn. The horn, the horn, awakes me at morn.

The drums playing two tones. They're always the same tones. The drums playing two tones. They're always the same.

It's from "Boy: Tales of Childhood", an autobiographical book by Roald Dahl.

She's talking about "Betsy-Tacy" and "Betsy-Tacy and Tib", the first two books in a series by Maud Hart Lovelace. They're about girls growing up in Minnesota a century ago.