Conversation so far:
Did the group influence many people?
they have inspired several notable musicians, including Rush, John Lydon, Marc Almond, Graham Coxon, Luca Prodan, Mark E.
Smith, John Frusciante, Bruce Dickinson and Julian Cope.
When was the group popular?
Though the group have generally been commercially unsuccessful outside of early 1970s Italy.
What type of music did they perform?
lovely sax-and-flute instrumental section.
Did they ever release any more music?
CANNOTANSWER.
Is there anything else interesting?
The Canadian new wave band Men Without Hats have a song titled "The Van der Graaf Generator Blues" on their 1991 album Sideways.

Question: In what other ways did they influence the sound of music?
Self-contained rewrite: In what other ways did the Van der Graaf Generator influence the sound of music?