The premiere of Tchaikovsky's E Flat Major Seventh Symphony was given by the Moscow Philharmonic under Terian on 7th February 1957. The American premiere was given by the Philadelphia Orchestra under Eugene Ormandy in 1962. The symphony was completed from sketches of Tchaikovsky by Semyon Bogatyryev who was a Russian composer and Professor at the Moscow Conservatory. Bogatyryev was born in 1913. He has composed two operas, two symphonies and a cantata. It took him about ten years to orchestrate from the sketches left by Tchaikovsky. He completed the work in 1956.
I am including the Ormandy (American premiere recording) and the Gennady Rozhdestvensky readings.