Following a recent Harmonix post about the viability of rhythm gaming on the PC, they have launched a crowdfunding campaign on Fig to bring Rock Band 4 and the Rock Band Network to Windows (thanks Doug). They explain this will be a port, which will allow their core engineering team to support them and continue their work refining the game, and their initial goal is $1.5 million. Here's more on their proposal:

The PC version of Rock Band 4 will have ALL the same content and features as the console versions currently do:

• World Tour Campaign Mode
• Freestyle Guitar Solos
• 65 songs included "out of the box" - and you can get up to 33 additional songs if you back us here on Fig!
• 1700+ additional playable songs available as downloadable content
• Supporting wireless guitar controller, drum kit and next generation microphone
• For more information, full song list and complete specifications, please visit http://www.rockband4.com

In addition:

• Tools to author your own songs for play in the PC version of Rock Band 4 - submit them to Rock Band Network via Steam Workshop and share with the rest of the Rock Band 4 PC community!
• Mouse and computer keyboard support for menu navigation
• All feature and content updates from the console game. Rock Band 4 on the PC will have all of the updates released prior to its launch, and will continue to be updated alongside the console versions moving forward.