Publishers churned out four-hand arrangements of almost every new orchestral or operatic work. These transcriptions often outsold the original full-orchestra scores.
This physical proximity was so striking that critics of the era sometimes referred to duet partners as "four-handed monsters," viewing the practice with a mix of fascination and moral suspicion. The Piano Duet
Before recordings existed, piano duets were the only way for the average person to hear massive orchestral works like Beethoven’s symphonies at home. The Piano Duet