In the series of articles posted recently, I mentioned a "Space Age" alternative to XYZ, especially over a 1NT rebid. Let's look at it.
The basic idea is to use the 2 Diamonds bid as a transfer, rather than an unspecified game-forcing bid. This is practical over a 1NT rebid because responder can assume the captaincy of the hand (over a rebid in 1 of a suit this is not as clear, and so I recommend trying this over a 1NT rebid only. You can extend it to other 1-level rebids later, if you want to).
The 2-level transfers are either sign-offs or game-forcing, since invitational hands always begin with the 2 Club bid (that forces 2 Diamonds from opener).
1 Club - 1 Heart
1NT - ?
2 Clubs - forces 2 Diamonds. (As presented in the prior articles. This bid will not be explained in the present post).
2 Diamonds - transfer to 2 Hearts.
2 Hearts - "transfer" to spades, i.e., 5 hearts and 4 spades, not forcing
2 Spades - This is a bit of an idle bid, but it is useful to play it as six hearts and 4 spades, game forcing. With 5-4 and a game force, you begin with 2 Diamonds, transfer to hearts. We will look at the next round after the transfer soon.
Others - as in XYZ.
The transfer must always be completed by opener, since one of its functions is placing the final contract in 2 Hearts. Once in a while (very rarely) opener will have a singleton and this contract will not be the ideal one, but you should not prepare your system to deal with that. Just as in a natural framework the rebid of responder's suit does not suggest any action to opener, the same principle operates here.
And so we can plan our auction very well after a transfer:
1 Club - 1 Heart
1NT - 2 Diamonds
2 Hearts - ?
You may be wondering what is the use of a transfer here when any heart contract is already placed in responder's hand. But this is not the sole (or even the most important) use of a transfer. The main gain is by giving leeway for responder to describe his hand, following the important principle that the unbalanced hand should describe.
Responder's rebids after his start will again use transfers to conserve space, starting at 2NT:
2 Spades: exactly 4 spades, GF. Does not promise 5 hearts. Does not deny it either. Opener will deny 4 spades or 3 hearts with 2NT; will show 3 hearts with 3 of a minor or 3 hearts (he bids his concentration of strength); or will show 4 spades by raising this suit.
2NT: transfer to clubs, GF. The idea is the same -- responder can have 4 hearts, or 5, or 6 (but cannot have 5 clubs, since he would use another sequence -- check the XYZ articles for how to bid with 55 hands). Opener raises clubs with 4, or bids 3 of anything with 3 hearts (denying 4 clubs), or bids 3NT with 2 hearts and 3 clubs. Note that responder can now bid 3 Hearts if he wants to show extra length there.
3 Clubs: transfer to diamonds, GF. Opener raises diamonds with 4, bids 3 of something with 3 hearts, or bids 3NT with 2 hearts and 3 diamonds.
3 Diamonds: Transfer to hearts. (Will these transfers never end?). This is a one-suiter looking for support. You may be looking only for 3-card support to choose the best game, or you may be slamish with a weak 6-card suit. A suit such as AJxxxx, KJ10xxx, and the like, in which the difference between 2 or 3 cards with partner is significant. Opener completes the transfer with 3 cards there, and bids something else with 2.
3 Hearts: Not a transfer (at last). This is a slamish one-suiter that is not concerned with length opposite. Opener reacts accordingly, ignoring his degree of support and evaluating whether his cards are good for slam or not.
Higher bids - voids. (The same bids directly over 1NT, without going through the 2-level transfer routine, show singletons).
In the next article we'll see these same principles applied to the 1 Spade response.