What Music On Hold is in VICIdial

Music on hold is the audio a caller hears when they are waiting and nobody is talking to them yet. In VICIdial it covers the silence that would otherwise sit between a call connecting and an agent picking up — when a caller is parked, queued in an Ingroup, or held during a transfer. Instead of dead air, the system plays a clip on a loop until something changes.

Under the hood this is an Asterisk feature, and VICIdial wraps a friendly admin screen around it. A Music On Hold entry — often called a class — is just a named collection of audio files plus a couple of rules about how they play. When a part of the dialplan calls for hold music, it asks for the class by name and the system streams whatever files that class points at.

Where the audio actually lives

A Music On Hold class does not store sound itself. It references files that already exist on the box. The files come from the Asterisk sound folders, and on a VICIdial system you usually push your own clips through the audio store so they land in the right place and pass format checks. Each entry then lists one or more of those files and a rank that sets the play order.

Format matters here as much as it does for every other prompt. Hold audio has to be the same flavor the dialer expects: PCM mono 16-bit 8k WAV or 8-bit 8k GSM. If you are fuzzy on which to pick, our breakdown of GSM versus WAV audio in VICIdial explains the trade-offs without the jargon.

How the dialer picks a class

Different parts of the system can each point at their own hold class. A Campaign can use one class, an inbound queue another, and a parked-call slot a third. When a caller hits a hold point, the dialplan looks up the configured class name, finds its file list, and plays them in rank order — or shuffled if random order is turned on. Here is the path from a waiting caller to the sound they hear:

flowchart TD
  A[Caller waiting on hold] --> B[Dialplan needs MOH]
  B --> C[Look up MOH class name]
  C --> D{Class active?}
  D -->|No| E[Fall back to default]
  D -->|Yes| F[Read file list and ranks]
  F --> G{Random order?}
  G -->|Yes| H[Shuffle files]
  G -->|No| I[Play in rank order]
  H --> J[Stream audio loop]
  I --> J
  E --> J

If a class is set to inactive, it drops out of the generated config and the system reaches for the default instead. That is why a quiet hold-music change sometimes shows up as silence — the entry got deactivated rather than edited.

Where it fits the bigger picture

Hold music is one slice of the audio layer that also includes greetings, voicemail prompts, and synthesized speech. If you want the full tour of how prompts and audio fit together across a campaign, start with our guide to VICIdial audio prompts, voicemail, and TTS. It ties the hold class into the rest of the caller experience, including how a DID (direct inward dialing) routes someone into a queue in the first place.

Once you know what a class is, adding your own is straightforward — you upload clips, create the entry, and point your campaign at it. VICIfast ships a fully configured dialer with the audio store and hold music wired up from the start, so see our pricing if you would rather skip the setup and start dialing.