ðə skˈiːm bˈeɪst ˌɔn ɹˈiːleɪz, wˌɛɹ wˈʌn pˈɑːɹtnɚ dᵻskɹˈaɪbz ɐn ˈæbsəns ʌv kəntɹˈoʊlz ɹˈæðɚ ðɐn pɹˈɛzəns, æz ɪn kjˈuː bˈɪdz, ɪz nˈoʊn æz spˈaɪɚɹəl skˈæn, ænd kæn biː kəmbˈaɪnd wɪð blˈækwʊd, ˈiːvən ɪn nˈætʃɚɹəl sˈɪstəmz.
The scheme based on relays, where one partner describes an absence of controls (rather than presence, as in cue bids), is known as Spiral scan, and can be combined with Blackwood, even in natural systems.