Tā zài gōngzuòshì lǐ shōucáng le bùshǎo lǎo héchéngqì.
He has a collection of vintage synths in his studio.
Tips
memory
合成 = 'synthesize / compose together', 器 = 'device / instrument' — a direct calque of 'synthesizer'. The same 合成器 shape appears for non-music senses too (e.g. 语音合成器 'speech synthesizer').
usage
In musician speech, 合成器 specifically means the sound-design keyboard (Moog, Roland, Korg, etc.) — distinct from 电子琴 (preset home organ) and 电钢琴 (digital piano).
