X is the tenth studio album by German composer and musician Klaus Schulze, released in 1978. The album features 6 musical biographies and is different from Schulze's previous works, being tense and anxious. It includes electronic instruments, percussion, and a string orchestra. The album is highly regarded by Schulze's fans and is often ranked in the top three of his albums. The album was recorded with some difficulties, including disagreements with the orchestras, which were resolved by cellist Wolfgang Tiepold. The album's lineup includes Klaus Schulze, Radio-Sinfonie-Orchester Frankfurt, Belgium orchestra, Wolfgang Tiepold, B. Dragic, and Harold Grasskopf.