space out

[Vladv1]

"When he wasn’t ‘fishing’ with Andy, Malcolm spent most weekends over at Kovac’s place, where the two would spend afternoons jamming together, "spacing out on" improvised jazz-rock fusions. ‘What a lot of people don’t realise is that Malcolm loved jazz,’ Kovac recalled. ‘From midday until six on Saturday and the same on Sunday, Malcolm would play nonstop jazz – all these jazz licks and jazz chords.’ Live, the less crowd-pleasing aspects of Malcolm’s love of jazz began to show itself in the band’s increasingly down-tuned sound".

Mick Wall, "Hell Ain't A Bad Place To Be".

What does "space out" mean here?

 

[emsr2d2]

It means that the act of improvising music together had a similar effect to drugs. It's usually used in the form of the adjective "spaced out".
Have you seen his eyes? He looks really spaced out.
I don't know what was in that tea but it made me feel very spaced out.

It's similar to being/getting high/stoned.