ちょっと一杯[chottoippai] let's have a quick drink
ばつ一[batsuichi] being once divorced
一向[hitaburu] nothing but
サラダ一皿[saradahitosara] plate of salad

安全第一[anzendaiichi] safety first
一か八か[ichikabachika] sink or swim
一っ走り[hitoppashiri] spin (as in 'take a car for a spin')
一つ一つ[hitotsuhitotsu] one-by-one

一弦琴[ichigenkin] single-stringed Japanese zither
琴線[kinsen] heartstrings
三角琴[sankakugoto] trigon (a musical instrument)
手風琴[tefuukin] accordion
心の琴線[kokoronokinsen] heartstrings

たて琴[tategoto] harp
風琴[fuukin] organ
木琴[mokkin] xylophone
提琴[teikin] tiqin (2 or 4-stringed Chinese instrument played with a bow)

一絃琴[ichigenkin] single-stringed Japanese zither
管絃楽[kangengaku] orchestral music
絃楽[gengaku] music for strings
絃楽器[gengakki] stringed instruments
絃声[gensei] sound of the strings

絃線[gensen] catgut
五絃[gogen] five strings
三絃[sangen] three-stringed instrument
絃歌[genka] singing and (string) music