air

airが気になりましたので早速手持ちの辞書を引いて調べてみますと、赤字の箇所は第七語義の「（（やや古））[音]調べ、旋律」（『ジーニアス英和辞典　第３版』大修館）となります。念のため英英辞典も参照してみますと’ a tune or short melodious song’Oxford Dictionaries Onlineと載っていました。(Shou-VR*)

I might have rebelled against these exasperating solos had it not been that he usually terminated them by playing quick succession a whole series of my favorite airs as a slight compensation for the trail upon my patience.

出典：Doyle, A. C. A Study in Scarlet. p.15