Complex sentence: Cale added piano, organ and celesta, against Drakes wishes at the time, although he was eventaually happy with the final product as the chronically shy and withdrawn songwriter formed a friendship and mentorship of sorts with Boyd.
Split into simpler sentences: Cale added piano, organ and celesta against Drakes wishes at the time. However, the chronically shy and famously withdrawn songwriter eventaually formed a friendship and and allowed a mentorship of sorts with Boyd.