The Opera Air Check Recordings collection comprises air checks of mostly Metropolitan and San Francisco Opera live performance broadcasts recorded on instantaneous discs, from 1937 to 1956, in addition to other unnamed orchestras from the same time period. Some of the conductors represented in these recordings include Bruno Walter, Arturo Toscanini, and Sir Thomas Beecham. Singers include Lauritz Melchior, Ezio Pinza, Jan Peerce, Lily Pons, Licia Albanese, Ljuba Welitsch, Zinka Milanov, among others. Many of the these broadcasts were sponsered by the Texas Company (Texaco) and carried on the Blue Network, with announcements and commentary by Milton Cross. The finding guide to this collection is available on the Online Archive of California.