Starting with OnSong 2020.7, only iOS and iPadOS 13 and higher are supported by the app. This brings up a couple of questions that this article will help answer.
May 2021 Update
Starting in April 2021, we have received reports that some users are unable to access older versions of OnSong 2020.5 as outlined in this article. We have contacted Apple regarding this issue as OnSong should remain available to users of older devices. OnSong makes all versions of the app available in a features of the App Store called "Last-Compatible Version" that states, "Some of your customers may not have a device that's compatible with your latest app version. To allow them to continue using your app, we make the last-compatible version of your app available to them."
Since that time it does appear that Apple has corrected this flaw and you should now be able to download and install older versions of OnSong on older devices.
I already have an older iOS device with OnSong
If you have an older device with iOS 12 or earlier, you should be able to update to the latest available version of OnSong for your device. However, you cannot receive future updates from either OnSong or Apple. We recommend upgrading to a newer iPad to receive continued support from Apple and OnSong as well as other apps and accessories. The standard 7th and 8th generation iPads are a great buy for around $300 and will give you years of support from OnSong and Apple.
I bought an older device and can't seem to purchase OnSong
We are not sure why this is the case with the App Store, but only the latest version of an app is available for sale on the App Store. You can't buy previous versions on older devices, and developers don't have a way to effect this. However, if you had already purchased OnSong in the past, you can install OnSong on older devices. The App Store will make the last known available app for that device available for installation.
While you can run older versions of OnSong on this device indefinitely, other integrations in OnSong, apps, and hardware may stop supporting the operating system without a means to update. It's recommend that you upgrade to a new iPad for future support.
Can I rollback to an older version of OnSong
The Apple App Store doesn't provide a way to roll back to an older version of an app that you've installed. We recommend that you disable automatic app updates to make sure they install when you have time to practice and ensure your apps and devices work together. This is common practice in the music industry. Likewise we recommend you hold off updating to the latest iOS/iPadOS versions for the same reason. While OnSong keeps up with changes in these operating systems, it can take time to ensure everything works with various integrations.
There are third-party solutions for saving various versions of apps, but this is a manual process and requires you to think ahead. One such product is called AnyTrans and you can learn more about how to save older version of apps to install later.