W-e-e-l-l, since I have a particular interest in this topic ("let the reader use discernment"!) I found this at the time particularly galling.
Downunder there were elements in the Branch Office who were jealous of the 'prominence' being gained by the man (a real pro) who gathered a national orchestra to play at large conventions. There was also the role later played by the branch coordinator at the time who himself gathered an orchestra for regular rehearsals at Bethel.
Why stop it? The official line was that it used up precious time that could (should?) be spent in field service. Yeah, right!
My own take on it is that basically, Dubs are anti-culture. It's not the first time in history when a religious organisation has outlawed music, or any culture for that matter. The Witnesses are no different. They (the hierarchy) just don't like (or should that be "understand"?) such things as music or the arts.
Imagine though what it's like for a dub who has musical gifts, how must they feel inside the confines of such an organsation? There are of course some Witnesses who pursue a musical career and quite successfully, but rather than their gifts being welcomed, the WT Society simply ignores them! How strange that the same god whom they claim to serve, has given such gifts and are ignored!
Contrast this with the fantastic bands and orchestras that lead church services. How is it that they get the musicians? Perhaps as a result of the anti-education doctrines that the WTS has long espoused. They reap as they have sown.