The Prelude and Fugue No. 4 - originally in C# minor, from the Well-Tempered Clavier (Book One) is not for the faint of heart (or the short of breath). It’s a gorgeous piece, but made up of long, slow phrases which can challenge the players. The fugue is over five minutes of a long, hard blow - but if the ensemble is up to it it’s really worth working up.
This piece is not published.
The Prelude and Fugue Number No. 4 sells for $20.00 for the hard copy and $15.00 as a pdf.
The mp3 performances are from my CD “Savannah River Brassworks,” available on my “recordings” page (link)