having two apps be "active", simultaneously?

hi everyone, I’ve got a Mac OS problem

I have a Mac Pro 2010 that’s running Moc OS 10.13 (High Sierra) with a USB extended keyBOARD (with a built-in numeric keypad) and an additional USB numeric keyPAD.

The thing is that I need to run two applications simultaneously and have my keyboard “attach” to one of the apps, and my numeric keyPAD “attach” to the other.

The two apps are; a music notation program - AVID Sibelius Ultimate 2023 and an audio player program - Amazing SlowDowner (ASD). Sibelius needs the full-size keyBOARD for input & control and ASD needs only the numeric keyPAD for start/stop/pause.

My work flow is; load an audio file in ASD, play that file and create notation in Sibelius. But my workflow’s constantly bogged down because with my current setup, I’m switching which app is “active” in order to get access to the app.

For instance, I begin by hitting a key on the keyPAD, which starts and audio file playing in ASD. Once it begins playing,I now have to use the keyBOARD to click in to Sibelius and begin entering notation. But, when I need to pause of stop audio playback, I have to move the cursor over to ASD and click to get it to stop or pause.

*IF* I could have both apps active and responding to their respective hardware’s, I could keep the keyBOARD controlled cursor on the music page of Sibelius - doing entries and edits - while controlling ASD with the keyPAD

I’ve taken a brief look at Split View, but I’m not sure if that will do it?

So thank you in advance for giving this a read. Perhaps it’s not possible to have two “active” apps at one time, but I thought I’d ask?