mouthpiece (n.)

• adviser
• advocate
• agent
• announcer
• annunciator
• attorney
• authority
• barrister
• bell
• bit
• channel
• civilian
• communicant
• communicator
• connection
• counsel
• counselor
• counselor-at-law
• delegate
• deputy
• embouchure
• extension
• front
• go-between
• gossipmonger
• grapevine
• herald
• horn
• informant
• informer
• intercessor
• intermediary
• intermediate
• intermediator
• intermedium
• internuncio
• interviewee
• key
• lawyer
• leader
• lip
• mediator
• medium
• middleman
• monitor
• mouth
• negotiant
• negotiator
• negotiatress
• negotiatrix
• newsmonger
• ombudsman
• phone
• pipe
• pleader
• press
• proctor
• procurator
• prosecutor
• publicist
• publisher
• radio
• rapporteur
• receiver
• reed
• reporter
• representative
• shyster
• silk
• slide
• solicitor
• source
• speaker
• spokesman
• spokesperson
• spokeswoman
• telephone
• telephony
• television
• teller
• tipster
• tout
• transmitter
• valve
• voice
• wind
• witness