It is possible to intepret signals from a standard, non-analog (and therefore significantly cheaper) usb-based gamepad and use a 49 toggle array as an interface. Of course, if an analog one is used, up to 64 toggles can be used.
The downside is that the array will produce blindspots if interpreted 'blindly'. In the image below, the three red points represent physical connections made in the array. The grey one is a 'phantom' blindspot- if the three red connections are made, the fourth will also be made automatically... the points are not independent as such, but are created by cross referencing two of the button on the pad. This method is similar to the Atari 2600 CX-50 keypad controller- where a matrix of three by four pins is used to get twelve inputs- and similar devices.
Clever programming on a case-by-case basis of use might be able to overcome some instances of this.
This system could perhaps be a cheap way to combine music and certain board games. But before I have a concrete idea, I am not going to venture down this thorny path...