關於巴洛克concerto

因進入20世紀之後,協奏曲的創作變得越發多樣,有按照傳統模式,亦有完全打破傳統結構的作品,這些叫做協奏曲的作品卻只有一件獨奏樂器而沒有樂隊,這不是叫做協奏曲,只是近似協奏曲這一體裁,如早就有巴哈的Italian Concerto

At Baroque Period, the composers wrote simple pieces.(Chamber music)

There was no big orchestra for a concerto, instead there were only a few instructments
accompanying the solo instrument (because the songs were often written for nobles to listen in a chamber, thus there was no reason for a big orchestra and this was called chamber music) , but as a piece with accompanyment other than piano is called concerto, these pieces are also called concertos.

2007-07-04 22:36:57 補充：
For the answer of the upper guy, there is a problem. "因進入20世紀之後,協奏曲的創作變得越發多樣,有按照傳統模式,亦有完全打破傳統結構的作品,這些叫做協奏曲的作品卻只有一件獨奏樂器而沒有樂隊,這不是叫做協奏曲,只是近似協奏曲這一體裁,如早就有巴哈的Italian Concerto ", but Baroque was in 17 to early 18 century...and Bach was a Baroque composer...