Something like the Raspberry Pi might work better It's got USB ports and a soundchip,
And, since it has a (multitasking) operating system you might run into latency issues (delay in the audio).
I'm not familiar with the Teensy, does it have one?
trigger them i remebered that i have an unused USB-Pad Controller (AKAI LPD 8
2.Whats the easiest way to connect the usb pad to an arduino and to read the signals it is sending.
I do not know if Teensy supports USB host MIDI.
There is built-in support for USB MIDI devices as well.