As for imposing is not uncommon in art music, especially in opera. Conductors also make changes in orchestration. Repeats, in say a symphony by Beethoven, are often omitted.
Regarding the Copland, the cuts in the finale are at a slow tempo and do make a difference. I would need to check the writing of Crist to see who made the two measure cut in the Koussevitzky performance. 
I am reminded of a Koussevitzky broadcast of the Diamond Second Symphony. Koussevitzky made a cut to accommodate the time allotted for the broadcast. For the non-broadcast performance, he played it complete. Bernstein cut it when he performed the work with the New York City Symphony.
It is because of Koussevitzky that we have the familiar ending of the Bartok Concerto for Orchestra. Bartok supplied it at the request of Koussevitzky. 
Composers often "approved" cuts. Consider what Sokoloff did with the Rachmaninoff Second Symphony. These cuts were supposedly done with the composer's approval. The cuts amounted to over 10 minutes worth of music. 
Consider the Gershwin Second Rhapsody. It is usually performed in the version done by Robert McBride. That version was done, to the best of my knowledge, after the composer's death. The composer's own orchestration is much more interesting. 
As to the ego of the conductor playing a part in this...well, you can look at it as a conductor's knowledge and perspective being a part of the process. Copland mentioned he was not totally appreciative's of Bernstein's cuts, but then Copland did write something like, "well he was probably right." Copland was very careful with what he did and would rarely revise...the Symphonic Ode being a major exception. But, it was Copland's choice to do so. Copland also reduced the size of the orchestra, making it less expensive to perform.
Even Toscanini made changes in orchestration.

    On Monday, February 22, 2016 10:32 AM, John Haley <[log in to unmask]> wrote:

 I wish you would do an article, Tom, setting forth all of those Mercury
facts you have put in this post.  Nobody else knows all these things the
way you do.

Re the Copland cuts, it is really astonishing today that a conductor
(Bernstein) would impose cuts of only ten measures (or in Koussevitzky's
case, only 2 measures), on a poor contemporary composer who is obviously
anxious, first of all, to get the work performed.  What possible
difference could it make to an audience to hear 10 (or especially two)
additional measures of music, as envisioned by the composer.  Even Szell
felt to urge to "improve" what Bartok wrote.  Imagine that.  I could
understand shortening a work by several minutes if is is getting dull
(although I would rather hear the piece myself to judge that), but whacking
out small numbers of measures seems like nothing more than the triumph of a
conductor's ego.  Don't you wonder about putting the shoe on the other
foot--how Bernstein would have reacted if another conductor had imposed
small cuts on his "serious" compositions?

John Haley

On Mon, Feb 22, 2016 at 6:36 AM, Tom Fine <[log in to unmask]> wrote:

> Hi Eric:
> I have no idea why Mercury used the various colored labels. It could have
> to do with what vinyl compounds were used, or the distribution lists, or
> something else. I am pretty sure that Mercury's Richmond plant, at least in
> the early 60's, used a quieter vinyl compound for the broadcast-only
> pressings. I have plenty of Limelight albums pressed there in the late
> 60's, with Broadcast Only labels, and the vinyl is awful, so apparently
> some Philips cost-cutter changed the protocol at some point. The early
> Richmond Mercury Living Presence cuts, the ones with "RFR" in the deadwax,
> generally aren't bad. I think a noisier vinyl compound was generally used
> for Philips USA pressings of the same era. The PHS90000/PH50000 series was
> cut at Fine Recording, from tapes sent over by Philips, and pressed at
> Richmond. The USA cover art and liner notes were original to this market,
> too. At first, after buying Mercury, Philips tried to establish a unique
> label/brand in the US market. They never put enough money behind it and
> never had any marketing skill, so it didn't catch fire. They pulled the
> plug on all of this by the early 70s, consolidating their classical record
> business in Holland. There is also some overlap in the Mercury and Philips
> classical catalogs. Mercury made a series of recordings for Philips, all
> released on the Philips label, in 1961 in England. And, in the SR90400
> range, there are some recordings from Philips released under the Mercury
> Living Presence label here. Mercury producer Harold Lawrence produced
> recordings for Philips, notably Colin Davis/LSO Handel Messiah. And, from
> 1965 on, Philips engineers made the Mercury recordings in England, using
> their own version of the 3-spaced-omni mic technique, which they called
> "M3."
> -- Tom Fine
> ----- Original Message ----- From: "Eric Nagamine" <[log in to unmask]>
> To: <[log in to unmask]>
> Sent: Monday, February 22, 2016 4:03 AM
> Subject: Re: [ARSCLIST] A couple of Mercury questions for Tom Fine
> Tom,
>> Thanks for the link to the Penndorf page. I'd forgotten about his work on
>> labels.  I found that he does mention that the colored labels were
>> promo/for
>> broadcast pressings in section 11. It's interesting that there were
>> various
>> colored promo labels when labels like Columbia generally only had white
>> label promos. I think that RCA had no promo labels only the "for
>> demonstration" stamp on the backs of their jackets. London only had those
>> round promo stickers on the front of the jacket.  I don't think I've ever
>> seen EMI or UK Decca promo labels.
>> Thanks to Karl Miller about the Copland 3rd. I guess I need to purchase
>> the
>> Pristine release of Carnegie Hall performance of BSO/Koussevitzky.
>> --------------------------
>> Eric Nagamine
>> -----Original Message-----
>> From: Association for Recorded Sound Discussion List
>> [mailto:[log in to unmask]] On Behalf Of Tom Fine
>> Sent: Saturday, February 20, 2016 3:00 AM
>> To: [log in to unmask]
>> Subject: Re: [ARSCLIST] A couple of Mercury questions for Tom Fine
>> Hi Eric:
>> I don't have answers to all your questions, but some info. See below.
>> -- Tom Fine
>> ----- Original Message ----- From: "Eric Nagamine" <[log in to unmask]>
>> To: <[log in to unmask]>
>> Sent: Saturday, February 20, 2016 3:21 AM
>> Subject: [ARSCLIST] A couple of Mercury questions for Tom Fine
>> Hopefully Tom can answer a couple of questions..
>>> 1.      I've been sorting through a deceased friend's collection and I
>>> noticed there were many different colored labels in addition to the
>>> normal
>>> Dark Plum or later Red labels. There's the common white label promo, but
>>> I've also found Pink, Green, Yellow and Gold labels in place of the
>>> normal
>>> plum or red labels on stereo SR series discs. Some say promo and some
>> don't.
>>> Any significance in this? I know some of the early mono Mercuries have
>>> the
>>> Gold Label and I think so does the Civil War sets, but these are not
>> those.
>>> First of all see this, from the late Ron Pendorf
>> Ron got his information directly from Harold Lawrence, so I assume it's
>> correct. Ron doesn't address
>> the green, pink and yellow labels I have seen from time to time. I assume
>> they have to do with
>> promotional or other uses. Ping me off-list with some deadwax info on
>> those
>> records and maybe we can
>> figure out some things. One thing I can tell you  is that the non-glossy
>> sleeves of early issues,
>> even if they have color printing on the back, indicate an inferior
>> pressing
>> from Mercury's own
>> Richmond IN plant. The best pressings, 1951 through about 1962, were done
>> at
>> RCA Indianapolis and
>> have an "I" somewhere in the deadwax. What has surprised me is how bad the
>> Richmond "for broadcast
>> only" white-label pressings are! Those were supposed to be the best vinyl,
>> for broadcast. The
>> examples I have did not shine a nice light on the quality of Mercury's
>> plant.
>> 2.      Do you know if the Dorati/Minneapolis Copland 3rd in the most
>>> recent Mercury box has the uncut version of the finale? From what I
>>> understand, every recording from the late 50's on use Leonard Bernstein's
>>> cuts from the late 40's, even the 2 Copland led recordings.
>>> I am not familiar enough with the work to know the answer. Here is a
>> video
>> said to be of that
>> movement:
>> BY THE WAY -- I can tell you that all the wow and flutter and distortion
>> you
>> hear in this lousy
>> transfer DON't EXIST in the new CD reissue, thanks to Plangent Process.
>> The
>> work is available in Box
>> Set 3 and as a 96/24 download from HDTracks. We also got a much more full
>> sonic spectrum, thanks to
>> Andy Walter at Abbey Road Studios. If there were enough potential sales,
>> and
>> thus interest from the
>> corporate parent, I'd remaster all the mono recordings the way we did
>> Copland 3rd.
>>> Thanks for any light you can shed on this.
>>> You're welcome!
>>> --------------------------
>>> Eric Nagamine