Gamma is a trump asking bid in Responder's trump suit (unless that suit is known to be of exactly 4-card length, when a 4441-shape hand has been described, in which case the Eta Ask is used). There are effectively 3 different scales for Gamma depending on whether or not the length of Responder's suit is known or not, and, if it is not known, whether this may be a 3-card holding in a Minor suit (ie: Forcing No Trump and Opener rebids 2♣ or 2♦).
In practice, the "length known" scale is rare in this system (over Weak 2's only), but is included for completeness. Gamma is normally used with 5-card or longer suits, but in the case of Forcing No Trump sequences where Responder is using Gamma in Opener's second suit they will sometimes be only of 4-card length. In this situations Responder should be aware that Opener might open a 5-card Major and rebid a 6-card Minor, so the responses to Gamma, which are open-ended, can become very expensive.
When is a Bid Gamma?
A bid is Gamma in the following situations:
After a 1♣ Opening and positive response in a suit, when another suit has not yet been agreed as trumps, a bid in Responder's suit is Gamma (eg: 1♣-1NT-2♠)
In any other sequence where Asking Bids have been established and no suit yet agreed as trumps, the first bid in Responder's suit below game level is Gamma (eg: 2♣-3♠(Alpha)-3NT-4♣)
In a Forcing No Trump sequence, a bid of the cheapest new suit over Opener's rebid is Gamma in Opener's Major.
In a Forcing No Trump sequence where Opener has shown a second suit, a bid of the 2nd-cheapest new suit over Opener's rebid is Gamma in Opener's 2nd suit.
There are a few other specific sequences (see the various Opening Bid pages) where a bid is Gamma (particularly over 1♦ and 2♣ Openings).
Responses to Gamma
There are effectively 4 different scales of responses to Gamma
"Length Unknown" Scale
This is the normal scale for Gamma and is used when the length of partner's suit is not known but is known to be of at least 4-card length:
: No Top Honours (any length)
: One Top Honour (minimum length)
: 2 or 3 Top Honours (minimum length)
: One Top Honour (min length +1)
: Two Top Honours (min length +1)
: Three Top Honours (min length +1)
: One Top Honour (min length +2)
...etc etc (open-ended)
"Length Known" Scale
This scale for Gamma is used when the length of partner's suit is exactly known and is longer than 4 cards. As stated above, this scale is generally not used in this system with the exception of Gammas over Weak 2 Openings.
: No Top Honours (No Repeat Gamma allowed)
: One Top Honour
: One Top Honour and the Jack
: Two Top Honours
: Two Top Honours and the Jack
: Three Top Honours (No Repeat Gamma allowed)
Forcing No Trump Scale
This scale for Gamma is used in Forcing No Trump sequences when Opener has rebid what might be a 3-card Minor (eg: 1♠-1NT-2♣) and Responder is making a Gamma Ask in that Minor.
: Any 3-card holding. (Suit is not agreed as trumps)
Now a further Relay by Responder is asking about the 3-card suit:
: No Top Honours
: 1 Top Honour
: 2 Top Honours
: No Top Honours (any 4+-card length)
: One Top Honour (4-card length)
: 2 or 3 Top Honours (4-card length)
: One Top Honour (5-card length)
: Two Top Honours (5-card length)
: Three Top Honours (5-card length)
: One Top Honour (6-card length)
...etc etc (open-ended)
"Set Up Suit" Scale
This scale is only used in two specific sequences where Opener has shown a setup 6+-card suit over a Forcing No Trump:
Here we have a assume that Opener's minimum holding is AKQxxx, and in the unlikely event that a Gamma Ask is required, the responses relate solely to the length of Opener's suit, ie:
Repeat Gamma Asks
Unless Responder shows all 3 Top Honours, or No Top Honours when their length is exactly known, Repeat Gamma Asks are permitted to clarify Responder's exact holding in the trump suit. These are allowed below game level only, unless slam values have definitely been established, in which case they are even allowed at game level. Sometimes a Repeat Gamma at Game level may be "ambiguous". There are four scenarios, depending on the scale being used and what Responder has shown in response to the first Gamma Ask:
Responder has shown no Top Honour, but length not known. Steps are:
: Minimum Length
: Minimum Length + 1
: Minimum Length + 2
...etc etc (open ended)
Responder has shown One Top Honour. Steps are:
: Q or KJ
: K or AJ
: A or QJ
If Responder has already promised or denied the Jack (ie: their length was known already) then they simply show which honour is held with the first of those alternatives.
Responder has shown Two Top Honours (or 2 or 3 Top Honours). Steps are:
: KQ or AQJ
: AQ or AKJ
: AK or KQJ
If Responder has already promised or denied the Jack (ie: their length was known already) then they simply show which two honours are held with the first of those alternatives
The Forcing No Trump Scale was in use and Responder showed a 3-card holding. Steps are:
: No Top Honours
: One Top Honour
: Two Top Honours
This takes care of times when Responder has a 5 or 6-card suit in the Minor that Opener bid on the second round, and Responder wishes to agree it even though Opener only has a 3-card holding. A Repeat Ask in these circumstances agrees the suit as trumps, but otherwise the initial showing of a 3-card holding does not mean the suit is agreed.
The use of Gamma always agrees Responder's suit as trumps. This agreement is only withdrawn if Teller shows No Top Honour and Opener immediately bids No Trumps (after a Major Suit Opening), or if Teller shows No Top Honour or only 1 top honour and only a 5-card suit and Opener immediately bids No Trumps (Gamma in a Major after a One Club Opening and a suit positive).
(eg: 1♣-1♥-1NT(Beta)-2♣(0-2)-2♥(Gamma)-2♠-2NT is handing over the Captaincy and withdraws the agreement of Hearts as trumps). In these circumstances Responder is free to show additional length and perhaps a semi-solid holding such as J109xxx(x) by repeating the suit, but otherwise would normally show a second suit or bid game in No Trumps if semi-balanced.
As a matter of tactics and probabilities, where Responder has shown a Major suit positive, it is almost always worth trying to fit in a low-level Beta before using Gamma (Unless Responder has 4+ controls, you will still be able to make the Gamma Ask at the 2-level. Where Responder has shown a Minor Suit positive, it is always worth making a low-level Beta first.
Responder should be aware that Opener may bid No Trumps naturally at the 3-level even if Responder shows a fairly strong/long suit. If Opener has made a low-level Beta Ask, then this sign-off should not be disturbed. If Opener has not, made a low-level Beta, however, Opener is normally simply showing a relatively minimum balanced hand with this sign-off and Responder is free to continue over 3NT if holding an stronger-than normal hand where slam is a decent possibility.
OCP System Change Log
Interference over 2♦ Openings (07-Apr-2017)
Completed documentation of interference immediately after Responder makes a 3-way Transfer, and also immediately after Opener either completes or denies a 2-way Transfer. This had never been fully documented before, so not repeated here. See the section on Interference on the Simple 2♦ page.
Gamma if Opener has a setup 6+-card suit (20-Mar-2017)
When the bidding has started 1♥-1NT-2NT(setup 6-card suit)-3♣(Gamma) or 1♠-1NT-2NT(setup 6-card suit)-3♣(Gamma), it makes no sense to use any normal scale for Gamma, because Opener is always showing a suit such as AKQxxx (or perhaps very rarely KQJ10xx). In these circumstances, however, we still need Gamma (1) to set the trump suit and get us into an Asking Bid sequence, and (2) to check on Opener's length.
The scale for Gamma that we now use is identical with the Repeat Gamma scale used when Opener has shown no top honour, ie: 1 step shows 6-card length, 2 steps shows 7-card length etc etc.
Responses to Two Diamond Opening (16-Dec-2016)
This is a major overhaul of the Simple System 2♦ Opening:
The 2♥ Response and continuations are largely unaffected, except that some hands that would originally have bid 2♥, now do something else.
The 2♠ Response now shows any 0-4 single-suited hand. Opener bids 2NT with a lower-range hand, but Oliver's Twist at the 3-level with an upper-range hand.
The Responses from 2NT through to 3♥ are now all 2-way transfers, showing either:
0-4 HCP with any any touching 2-suited hand or even 4333 or 5332 where the suit above their 4+-card suit is at least 3-card in length, or
14+ with any 2-suited hand, normally transferring into the cheapest or lower-ranking suit, but optionally into the high-ranking.
Opener completes the transfer with a 4-card holding in the transfer suit and relays in the suit above with a singleton in the transfer suit. If Opener bids the transfer suit, Responder normally passes with any 0-4, but with 14+ treats the bid as Gamma. If Opener skips the transfer suit, again Responder normally passes with 0-4, but with 14+ bids their second suit as Eta (Cheapest bid in NT's normally is Gamma in the suit Opener actually bid.
For full details, please see the re-written 2♦ page.
Interference over a Positive Response to 1♣ (01-Oct-2009)
The use of D1P2/R1P2 and backwards Asking dates back to the original description of OCP in the late 1980's. Opener's action after interference immediately over a Positive response to 1♣, however, has always been somewhat different. Prior to 2009, there was a long list of what Opener should do depending on what the Positive response showed, and what the interference was and what it showed. This was difficult for everyone to learn and remember.
In 2009, following the advent of Relay Beta in 2008, that list was scrapped and replaced by four simple rules:
If Responder showed a balanced hand, then over the interference, Pass was Beta and Double an Ask in the suit below the last suit bid.
If Responder made a Positive showing a 5+-card suit, then over the interference, Pass was Gamma in Responder's suit and Double an Ask in the suit immediately below the last suit bid.
If a cheap Gamma was available as a relay over the interference, then that was used for Gamma and Pass was an Ask in the suit two below the last suit bid.
In the event of pre-emptive interference overthe positive response, then Pass was reserved at Lebensohl (forcing a Double), and Double was now Gamma or Beta, depending on whether Responder had shown a suit or not.