New Complete Edition
The New Complete Edition (NCE) of Tchaikovsky's works was launched in 1993 on the centenary of Tchaikovsky's death. It was to be published jointly by Schott (Mainz, Germany) and Muzyka (Moscow, Russia), with the textural portions of presented in both English and Russian. The editorial board included Professor Dr Lyudmila Korabelnikova, Dr Valentina Rubtsova, Dr Polina Vaidman, and Professor Dr Thomas Kohlhase.
It was intended to overcome the deficiencies of the old Complete Collected Works, which had been published between 1940 and 1971 (volumes 1 to 62), with an additional volume on church music released in 1990 (volume 63). In the old edition some of the texts set to music by Tchaikovsky were changed by the editors for arbitrary ideological reasons, and quotations from the old Russian anthem were also replaced by other music. They omitted, amongst other things, the full score of the opera Vakula the Smith, Op. 14, the unfinished Symphony in E-flat major, and Wilhelm Fitzenhagen's version of the Variations on a Rococo Theme, as sanctioned by Tchaikovsky. Moreover, no uniform editorial standards were applied to the text or music, and there were no detailed critical reports, comprehensive descriptions of sources, or thorough evaluations of the manuscripts and alternative readings.
The New Complete Edition would address all of these defects, with the aim of including the composer's final intentions together with alternative and earlier versions of works, as well as fragments and unfinished works, in reproductions that were faithful to the original sources, and which would be fully documented and discussed in the critical reports, with the objective of producing an historical-critical edition intended to be used both for research and for performance.
In addition to the 76 music volumes (Series I to X), including prefaces and critical reports, Series X would include facsimiles of Tchaikovsky's surviving sketches, as well as a commentary; Series XI would include his writings, diaries, letters and correspondence; Series XII would comprise a thematic catalogue  and Tchaikovsky encyclopaedia.
Since 1993 the following volumes of the New Complete Edition have been published:
Vol. 39a. Edited by Polina Vaidman (1999)
Vol. 39b. Edited by Thomas Kohlhase, with the assistance of Polina Vaidman (1993)
Vol. 39c. Edited by Thomas Kohlhase, with the assistance of Polina Vaidman (2003)
Vol. 69a. Edited by Lyudmila Korabelnikova and Polina Vaidman (2008)
Vol. 69b. Edited by Thomas Kohlhase (2001)
The fact that so few volumes of the New Complete Edition have appeared since 1993 can primarily be attributed to the fact that so far no government funding for the project has been forthcoming, unlike the situation with comparable editorial projects (e.g. the complete works of Schubert, Schumann, Brahms, Richard Strauss, etc.), where it has proved essential. Without the facilities to examine all the sources, and to prepare the editions in collaboration with external editors, archives, researchers, editors, proof readers and publishers, the New Complete Edition could not be continued 
On 7 June 2018, Schott announced that the Academic Edition of the Complete Works would be "the legitimate successor to the previous endeavours for the publication of the complete works of P. I. Tchaikovsky and the project of the New Complete Edition initiated by Schott Music in 1993", and that as from 2018 they would become the international distributors for the Academic Edition in collaboration with MPI Music Production International in Chelyabinsk .
Notes and References
- The thematic catalogue was published separately, in Russian and English, as (2006), edited and compiled by Polina Vaidman, Lyudmila Korabelnikova and Valentina Rubtsova.
- Information received from Dr Thomas Kohlhase, June 2014.
- See: https://de.schott-music.com/wp-content/uploads/2018/06/Tchaikovsky_A4_Subsriptions-Flyer_low_res.pdf