Tenor and bass trombones are found in an orchestra, though some pieces call for an alto as well.
at least 2 trombones.
In a symphony orchestra in the brass section there are usually 3 trombones in proportion with 4 horns, 2 trumpets and a bass instrument. ref The Oxford Companion to Music, orchestra, page 898.Most of the time, an orchestra uses three trombones, with two tenors and one bass.
Most of the time, an orchestra has three trombones, where it's two tenors and a bass.
Tenor and bass, but there is sometimes an alto trombone too. In a section of three trombones, there will either be one of each, or two tenors and one bass.
At least two french horns, four trombones, four trumpets, and two tubas.
2-3 trombones alone, or 3 trombones with 1 tuba.
Trombones contain copper and zinc (two elements) in an alloy we call brass.
Yes. There would often be two horns and two trumpets. Trombones were added in the late Classical period. The tuba wasn't invented until the 1840s, well into the Romantic era.
two or three
One or two are usually sufficient.
Only for the largest works. Most symphonic works require only two or three trombones.
On the low end, there might be two horns and two trumpets. On the large end, there are four horns, three trumpets, three trombones (2 tenor, 1 bass), and a tuba. Some pieces, such as Mahler or Bruckner symphonies, use even more instruments than that.