The latter is somewhat unusual as parts of the performance have been recreated via computer. This is what AllMusic has to say:
For many serious jazz fans, no pianist has ever approached the technical mastery of Art Tatum, though his virtuoso skills usually meant he was at his best unaccompanied. Many of his recordings from the 1930s & ‘40s were limited by the deficiencies of recording methods at the time. Piano Starts Here, long considered 1 of Tatum’s definitive albums, combined 4 solos from a 1933 studio session (his 1st as a soloist, aside from a test pressing a year earlier), & a fabulous solo concert at the Shrine Auditorium in 1949 (the latter issued as an Armed Forces Radio Service 16" transcription disc), which has been reissued many times over the decades. But there were several problems with these releases. The pitch was slightly too slow on the live material. A medley of George Gershwin tunes was awkwardly edited (a miserly decision to save on royalty payments) to only “The Man I Love,” discarding over 1 minute of other compositions, including “Summertime,” "I’ve Got Plenty of Nothin’," & “It Ain’t Necessarily So.” The order of the live performances was also altered.
Zenph Studios decided to use 21st century computer technology to re-create this album, both the 1933 studio session & the famous 1949 concert. The technicians worked wonders with the source material, by correcting the speed & adding the missing segments. Improvements in computer technology enabled the staff to not only replicate how Tatum played each key, but also to duplicate his use of the sustain pedal, recording the playback on a MIDI file that in turn served as source for a Yamaha Disklavier Pro concert grand piano, which was recorded 2 different ways on the very same Shrine Auditorium stage. They even took the time to duplicate the exact location of the piano on-stage for Tatum’s original Shrine concert. No audience was used for the 1933 selections, which included versions of “Tea for Two” & “Tiger Rag,” in all likelihood similar to the performances Tatum used to best both Fats Waller & James P. Johnson during a Harlem cutting contest not long after Tatum arrived in New York City. Of major interest is the greatly improved fidelity of the re-creation of the 1949 concert. Instead of using generations-old, flawed tapes that were descended from the original AFRS transcription disc, the MIDI file as played back on the Yamaha Disklavier Pro concert grand piano seems closer to the essence of what Tatum’s original performance sounded like.