Final answer:
The specific length of Ornette Coleman's 'Free Jazz' is not provided in the references, and such improvisations typically varied in length. 'Free Jazz' embodied spontaneous musical creation without set time frames.
Step-by-step explanation:
The improvisation you're asking about, known as "Free Jazz", refers to a groundbreaking jazz piece by Ornette Coleman and his double quartet. Unfortunately, the provided references do not contain specific information regarding the length of Coleman's improvisational piece.
Typically, 'Free Jazz' was not restricted by traditional forms or established time frames, focusing instead on the spontaneous creation of music without predefined structures. The improvisation length could vary considerably from performance to performance, reflecting the essence of jazz music's evolution during the 20th century.
Moreover, 'Free Jazz' by Ornette Coleman is not directly related to the improvisation referred to in the references such as Improvisation 28 by Kandinsky or the early 20th-century jazz bands mentioned.