Video chat software and services handle conversations well, but there is just enough time lag in them that it's difficult for users to play music with one another. (Evan Ramstad — AP/The Minnesota Star Tribune)

After last week's column on PC and Mac video calling (see tinyurl.com/v4zeggr), several readers wanted to know if the sound quality could be improved. Dale Lewellyn of Bloomington wanted to know if sound could be adjusted so people could hear one another at the same time. Marcia Edwards of Brownsville, Texas, wondered what could be done about the time lag on video calls that prevents playing music with friends. Peter Brennan of Minneapolis asked if video calling services offered a "virtual room" where all musicians could hear one another without any time delay.

A: There are a couple of factors involved in video call sound quality — the technology being used by the video calling firm, and the unavoidable time lag in video conferencing.

• Some video calling services, such as Zoom, support what's called full-duplex audio. Full duplex means that sound simultaneously travels both ways, so people on either end of the video call can speak (or sing) at the same time. Other services, such as Skype, support only half-duplex sound, so only one person can talk at a time.

• Time lag — the delay between when one person on a video call speaks (or sings) and the other person hears it — is a significant problem for musicians.

Zoom has said that it tries to keep video calling time lag (also called latency) to about 150-thousandths of a second (also called 150 milliseconds), a level at which it isn't very noticeable for speaking.

But music is different. Music experts say that a time lag of seven-thousandths of a second can affect a performer's ability to stay with the beat, and that a delay of 15-thousandths to 30-thousandths of a second will be noticed by listeners (see tinyurl.com/y8kzjp3x).

Video call time lag is caused by three things: how long it takes a signal to travel through your internet service provider and across the internet; how long it takes video calling software to process the data; and how fast your home network is. The only one of those you can optimize is your home network (see tinyurl.com/rxnj8a7).

Unfortunately, the video calling services don't have an online "virtual room" where musicians could perform together without any time lag. The closest thing to it are "collaborative apps" that let musicians share or combine their own recordings through a central website (see tinyurl.com/yd5a2bvl).

Reboots

Last week's column listed the wrong website for downloading the Mac version of Facebook Messenger, which enables video calling. You should instead download it from the Mac App Store. My apologies for the mistake.

If you downloaded a Mac program from the incorrect website, you need to get rid of it. It's not the real Facebook app and contains "adware" that will display unwanted advertising. Rather than simply uninstall it, download the free version of Malwarebytes (see tinyurl.com/jf29qxx). Let it scan your Mac, then click to "quarantine" any malware it finds.

In an earlier column (see tinyurl.com/w9nfszy), the web address of RetroFloppy was garbled. RetroFloppy (tinyurl.com/ubb4jqp) converts old computer disk files to modern storage formats.

E-mail tech questions to steve.j.alexander@gmail.com or write to Tech Q&A, 650 3rd Av. S., Suite 1300, Minneapolis, MN 55488. Include name, city and telephone number.