This Drexel professor’s free app allows choir members to create music together, remotely

Drexel University professor and technologist Dr. Youngmoo Kim sings in an a cappella group in his free time and was looking for a way members of his singing group could still create music together while practicing social distancing during the pandemic.

After looking around the Apple App Store, he didn’t find any solutions. That gave him the motivation to create Virtual Chorister.

As a musician, Kim found unique challenges that affected the way chorale members tried to create music when separated — differences in internet speeds could cause delays when recording the same music, for instance. Also, Kim found that several of the singers trying to record their chorale parts were using two devices at once, and he realized that many people don’t have the resources to do that.

In trying to make the experience of recording chorale parts easier, Kim was able to focus on how people create music, first.

“This is about singing,” said Kim, founding director of the cross-departmental ExCITe Center, which intersects art and science. “This is not about being a technologist. A lot things written by technologists are not for regular people. This was my way of making things easier. This is a great way to keep singing through the pandemic. Nothing beats being onstage for a chorale singer, but this is a way that we can continue to collaborate, express ourselves and do things musically.”

Through Virtual Chorister, a conductor or choir director can provide a reference video with which choir members can synchronize, and after recording their part, choir members can upload their video to the app. Once every member’s section is uploaded, a user can combine every section to make a complete recording.

Kim has extensive experience in designing music software, thanks to a previous role with Digidesign where he designed plug-ins for ProTools, a benchmark recording software that revolutionized the music industry. To code Virtual Chorister, he used XCode to write the app in Swift using standard iOS software development kit SDK.

For Kim, designing an app that could help vocal musicians sing remotely with each other was also a challenge to basic laws of physics. Kim explained that electrical signals are less resilient as the distance separating them increases and as a result, the best way to collaborate remotely is within 100 miles. While Virtual Chorister does not overcome the 30 millisecond delay limit, he wanted to create an app that could come as close to doing that as possible.

“We have experimented with systems that let you do things in real time over the internet,” he said. “If you can get less than 30 milliseconds [of delay], it would almost work. It’s about the delay you would get onstage from one end to the other. It’s tolerable, but even if you have a good internet connection, keeping it under 30 milliseconds is hard.”

Kim is a proponent for helping communities affected by the digital divide find solutions. Making the app available for free was an intentional decision so that it could be accessible to school choirs and other groups that may lack funding.

“School choirs and youth choirs are facing an enormous challenge this year,” he said. “This is a free app and hopefully helps more school conductors and music directors that want to get over speed bumps and challenges. It’s very doable, it just takes a little bit of know how.”

Virtual Chorister is currently only available on Apple iOS, but Kim is open to collaborating with Android developers to create a version for Android devices.

Michael Butler is a 2020-2022 corps member for Report for America, an initiative of The Groundtruth Project that pairs young journalists with local newsrooms. This position is supported by the Lenfest Institute for Journalism.