The Alternating tandem reel of three is a common derivative form of the simplest form of Tandem reel of three (only one Dancer replaced by two in Tandem) in which the Dancer following in Tandem overtakes the leader on reaching the End of the Reel of three; on reaching the other End of the Reel of three, the lead changes again.
In bars 9-16 of the Scottish Country Dance, The Flight of the Falcon, 1st Couple Dance an Alternating tandem reel of three on the First corners' Diagonal, 1st Man leading when Travelling Diagonally Down, 1st Lady leading when Travelling Diagonally Up. It is particularly important that the leading Dancer should make a large loop so that the following Dancer can pass on the inside and so take the lead, easily.
In almost all examples, (except while overtaking) the following Dancer Travels on the same path as the leading Dancer, about one step behind. However, in Dancing Dolphins, the deviser specifies that they should Cover parallel to the Sidelines, Man Above Lady throughout these Reels of three. This Covering has the two Dancers equally spaced on a line parallel to the axis of the Reel of three, with the midpoint tracing the path which the replaced single Dancer would have followed; arguably, this should be the rule for all forms of the Alternating tandem reel of three.
The Alternating tandem reel of three also occurs in the half form as, for example, in bars 9-24 of Pelorus Jack, successively on the First corners', the Second corners', the First corners', and the Second corners' Diagonals.