There's a website that allows you to search for an item of classical music by playing the basic tune on an online keyboard.

This churned out SCHUBERT, Franz Peter (1797-1828)
Title: Symphony No.5 in Bb, D.485, 3.Menuetto. Allegro molto - Trio

I can't find any sort of preview link to see if it is the one I have been after for several years now, and there's no guarantee I played it right but the only assistance I can give is that it is a well known and sinister sounding piece which is often associated with imagary of the industrial revoloution, chimneys being demolished and steam engines etc...

Do you know the one I mean?

It's the one that goes, 'DA DA-DA DA-DA DA-DA DA-DA DA-DA DA-DA, DAAAA! DA-DA DA-DA DA-DA DA-DA DA-DA DA-DA, DAAAA, DAH DAH DAH DAH', well you get the idea.

This is a long shot but you never know.