Thinking about Qwertet? Its Fourths & In-Key chord modes need your keyboard to register several keys at once — and most keyboards, even Apple's Magic Keyboard, can't: tightly clustered keys "ghost" and block each other. For basic playback, this can be fine, but you can check your keyboard's chording ability here before you buy to validate complex, virtuosic playback styles. Connect your hardware keyboard, click this page once, then hold the combos below.
Unfortunately, if you can't hold these chords, it's a limitation of your keyboard — not something that can be resolved in the app. Apple's Magic Keyboard handles spread-out combos but still ghosts on tight vertical clusters; true N-key rollover is mostly a gaming-mechanical-keyboard feature. What still works on any keyboard: the on-screen touch keys (touch never ghosts), LOTUS mode, where a full chord comes from a single root key, and any chords your keyboard passed in the test above.