There are two main reasons why you would be hearing hold music playing in your conference call and one less common reason.
1. You have the Waiting Room feature active
When the Waiting Room is turned on, all participants will hear hold music and the call won't begin until someone joins your meeting as moderator. This means that someone must call in using their moderator PIN or the organizer of the meeting needs to be logged into their account before joining via internet. If you don't need the Waiting Room active, you can easily turn off this feature for future calls via the 'Settings' section of your account.
2. There is only one person in the conference call
With any conference call, the first participant will always hear hold music. Even if it is the moderator who calls in first, the music will play until at least one other participant joins the meeting. If you prefer that there is no hold music playing when just one participant is present on the line, then you can turn this off via the 'Settings' section of your account under 'chimes & name announce'.
3. There is a participant who has call waiting or perhaps hooked their line
On rare occasions a participant may receive another call on their phone and place the conference line on hold. This will mean that their own hold music will play to all participants. This is easy to fix while a call is in progress. Just press *7 as moderator to mute everyone. Then have the individuals who need to speak press *6 to unmute their own lines. Or you can also mute the caller who is causing the interference using the online meeting room.