What phone system is playing that hold music? Name the sound, identify the PBX, and learn the weird history behind it.
Every phone system has a sound it makes when it puts you on hold, and that sound tells you what’s running the switch. Cisco’s is a teenager’s 1989 synth practice tape. Avaya IP Office’s is a 425 Hz beep that everybody mistakes for a fault. For plenty of older systems it was just a radio duct-taped to the wall of a phone closet.
This is a field guide to those sounds. Every claim links to a manual, vendor doc, or published source. Anything we couldn’t pin down is marked that way, not guessed.
Answer two quick questions and we'll narrow it down. Tap ▶ on any match to compare.
REAL RECORDING the actual shipped audio, legally shareable · RECREATION synthesized by us to documented specs, through a simulated 8 kHz phone line
1998 onward. Files on a server, and the famous defaults.
The one everybody knows: Opus No. 1, a teenager's 1989 practice tape.
Cisco's router-based small-business phone system. No Opus No. 1 out of the box.
The open-source PBX. Its five bundled hold tracks are Creative Commons, so you can hear the real ones here.
A web GUI on top of Asterisk, with the same five default hold tracks.
No music at all by default: a 425 Hz double beep every few seconds.
Mitel's IP platforms. The sister product MiVoice Office 400 documents a double ringing tone; MiVoice Business is unconfirmed.
ShoreTel shipped a built-in stock hold track. Nobody seems to know its name.
Software PBX that ships one stock file, literally named onhold.wav.
Small-business IP PBX with one electronic hold track in the box.
Asterisk-based appliance with a five-file default hold class.
Microsoft's on-prem UC stack shipped two hold files: DefaultHold.wma and cpsmoh.wma.
Stock tracks from vendors who mostly won't say what they are.
Teams ships a royalty-free default hold track. Microsoft doesn't say what it is.
Cloud phone service with selectable stock hold music.
Zoom's cloud PBX ships a default hold audio in its asset library.
1960s–2000s. Mostly: bring your own radio.
The Bell System's relay-driven button phones. Hold meant silence unless someone added a card.
America's small-office phone system. The manual tells you to plug in a radio.
Big-iron AT&T PBXs whose software lives on as Avaya Communication Manager.
Northern Telecom's enterprise digital PBX line, from the 1975 SL-1 to the CS1000.
The small-office Nortel system, where 'On hold' is literally Music, Silence or Tones.
Mitel's workhorse digital PBXs, with music on hold through an optional add-on card.
The rare old system with REAL built-in hold music: Medley A (folk songs) or Medley B (Christmas).
Panasonic's small-office systems. The 'built-in Panasonic melody' isn't in the manual we checked.
Toshiba's long-running key systems, with a dedicated MOH port for an external player.
Silicon Valley's PBX pioneer and its Siemens successor. Music needed a transformer box.
Samsung's manual says it outright: the default music source is NONE.
Things everyone remembers that the manuals don't back up.