Glass Enclosure

Powell had been in a mental institution until six months before the recording session.[2] He was contracted to play at the Birdland jazz club in New York, and its manager was Powell's legal guardian.[2] He kept Powell locked in an apartment to ensure that the pianist would play at the club.[2] According to Blue Note producer Alfred Lion, who went to the apartment one day, "There was a piano there and [Powell] played me some new things. One piece really stood out. I asked him what he called it. He looked around the apartment and said, 'Glass Enclosure'."[2]

Alternative explanations for the title have been proposed by critic Kevin Whitehead: it could have been for the announcer's booth that was beside the stage at Birdland, "or maybe the invisible box that walled Bud off like a trapped mime."[3]

"Glass Enclosure" is stylistically different from Powell's typical compositions,[4] which were often more conventional bebop numbers.[2] Leonard Feather wrote in the original album liner notes that "'Glass Enclosure' is more or less in four movements: the first somewhat maestoso, the next a swinging format on two 10-bar phrases: then a pensive yet flowing movement with a stirring bowed-bass underline, followed by a reminder of the first movement".

Author Francis Davis states that "'Glass Enclosure' juxtaposes to harrowing effect an agitated blues riff and a ten-bar fanfare".[2] It "runs through a sequence of abrupt changes of mood and direction", described by critic Kenny Mathieson as "disturbing, unsettling fantasia".[4]

The musicians for the original performance were Powell (piano), George Duvivier (bass), and Art Taylor (drums). Duvivier had taken over as the bassist in Powell's trio probably around a month before the recording.[4] Davis indicated that the piece was entirely composed,[2] while Mathieson suggested that the composition leaves "little scope for improvisation".[4]

Davis suggested that "This piece has to be played Powell's way or not at all, which explains why it's so rarely performed."[2] Powell himself also played the piece in public.[5][6]

Saxophonist Wayne Shorter was influenced by the more advanced harmonies used in "Glass Enclosure" and other Powell compositions from the 1950s in his own writing of music.[7] A Shorter biographer observed that, although "jazz musicians didn't start playing Lydian augmented chords with any frequency until the 1960s, Bud Powell played a few on 'The Glass Enclosure' in the early fifties."[8]