Stage Tour supports solo play and cooperative local or online multiplayer, including cross-platform play.
Local and online co-op
The official description supports taking the stage solo or with a band through local or online cooperative multiplayer. Steam also lists shared/split-screen and online multiplayer features.
Mix instruments
Players can mix and match Lead Guitar, Groove Guitar/Bass, Drums and Vocals in any combination. PC Keyboard and gamepad are also confirmed input options for Arcade Mode.
Cross-platform status
Cross-platform cooperative play is explicitly confirmed. The official pages have not yet explained invitations, account linking, voice chat or whether every mode uses the same crossplay rules.
Player-count caution
Steam references play with up to four players, but final per-mode local and online limits should be rechecked at launch. This guide does not assign unsupported player counts to individual modes.