From the Railway Preservation Society of Ireland website:
Belfast Central to a Mystery Destination & return!
Depart Belfast Central at 7:20pm, returning at 11:45pm.
Get out the glad rags, dust off the straw boater, its Jazz time! Join our restored 1960's steam train from Belfast Central, relax as we leave the city behind and enjoy the sounds of New Orleans jazz from the Apex Jazz Band as we pause at stations throughout Northern Ireland.
All Tickets: £24
Tickets can also be booked (by phone or over the counter) at: Belfast Welcome Centre, 47 Donegall Place, Belfast, BT1 5AD.