Changed Waiters

A position in which every black move has a set white continuation is known as a complete block.  To solve such a problem one just needs to find a white move that preserves all of these set white moves - a waiting move.  Sometimes there is not waiting move to be found and one has to change one or more of the mates.  If there is no threat after the key then such a problem is called a changed waiter or mutate.  The Warton brothers specialized in changed waiters and their work is represented below.  Since I love mutates (who doesn't) I have selected several problems.   As usual we begin with one of my own.  

Moen, Kabe
Original 2016

#2

6 + 5

Here is a simple mutate that was made by modifying one of my other problems.  The set play is as follows:
     1...Qd4,Qd3,Qd2 2.RxQ
     1...Qxd1 2.Rxd1
     1...f5 2.Bxe5
No waiting move is available so one of the mates must be changed.  The nice key 1.Rh1! unguards e5 to access the sixth rank.  1...f5 2.Rh6.   There is  not a lot of play but the position is elegant and open without any white pawns. 

Shinkman, William
1900??

#2

4 + 2

We begin with a very simple miniature from the Wizard of Grand Rapids that will give you a taste of what mutates are about.  Black has one move, 1...Sg6, to which white can respond with 2.Qxg6#.  However, there is no waiting move available because any move by white will either free the king or unguard g6.  Instead a new, pure, mate (each square in the kings field is covered only once) is arranged that uses the knight to self block on g6.  

Mansfield, Comins
The Observer 1919

#2

6 + 4

Here is an elegant example from Comins Mansfield.  The key only changes one mate but the change is a nice one.  The R+P battery changes gets swapped for a royal battery.   Click on the diagrams solutions.

D'oily Bernard, Henry
Grantham Journal 1928

#2

9 + 9

Here is a beautiful changed waiter.  It seems that there should be a waiting move that preserves all of the set mates yet there is not. The bQ controls the squares d3 and e6. If she moves then she will lose her control over these squares (focal play).  If the bP on a7 or bS move then they will interfere with her lines.  In either case the wS will be able to mate on the critical squares.  The key abandons this plan by giving up the guard on e4 and changing the foci to f1 and f6.  All while sacrificing the wR in the process.

Warton, Joseph and Warton, Thomas
Western Daily Mercury 1918

#2

9 + 10

A classic Warton brothers problem.  The key changes two of the mates.  The bishop hides behind the queen to take over pinning duties for the queen which now can be pinned herself.

Warton, Joseph and Warton, Thomas
The Observer 1942

#2

9 + 10

Another Warton brothers classic.  Again, only one change but a beautiful one.  The set double pin mate gets changed into a Gamage unpin.  

Bwee, Touw Hian
Die Schwalbe 1967

#2

8 + 8

One of my favorite changed waiters in terms of surprising change.  The R+P battery gets swapped for a Bristol clearance.  

Bwee, Touw Hian
Sinfonie Scacchistiche 1967

#2

8 + 10

Here is a tour de force.  The key changes all four set mates, sacrifices the wSe3, and adds a mate.  

Warton, Joseph and Warton, Thomas
The Observer 1946

#3

5 + 7

We end with one of my favorite three movers of all time.  Notice that the wB on e1 is ready to mate with BxR as soon as the bB on h2 relinquishes its guard on the g3.  The bB on h7 gives black an extra move.  However, any moves by bBh7 lead to an immediate capture by the wB, wK, or wS on c5.  This is the grab theme and in this case a complete block.  No waiting move that preserves these captures is to be found.  What remains is to give the bB the square f5 while closing the other line for the bR for: 2.Ba5 ~ 3.Bd8#.