Midi Problem With Sustain Pedal, Pedal Plays Note Options

[brunomb]

I am using a MIDI to USB adapter to connect a Yamaha P-155 Keyboard to a Macbook laptop. The adapter works in Garageband and Synthesia. The sustain pedal on the keyboard is not working properly with this setup. Instead of sustaining the notes, when I depress the pedal it plays a note by itself and mixes up different sounds. I don't have experience with MIDI so am clueless as to what is happening. Any help is appreciated. Thank you.

EQUIPMENT

• Yamaha P-155 Keyboard
• Apple Macbook dual 2.4 Ghz 2010 model
• Unbranded USB to MIDI adapter (http://www.amazon.co.uk/gp/product/B004IJ5FEU/ref=oh_details_o00_s00_i00)

SOFTWARE

• Garageband 2011
• Synthesia
• MAC OS X Lion 10.7.4

[brunomb]

I've partially solved the problem by unplugging the MDI IN cable to the keyboard (=MIDI OUT from the computer). What seems to be happening is a cumulative effect between 1) and 2) whereas 1) depressing the sustain pedal is causing a note (E3 or E4) to be played, and 2) there seems to be some effect of a MIDI feedback loop where the sound goes from the keyboard to the computer, back to the keyboard and so on. Unplugging one of the MIDI cables as stated above seems to have reduced the MIDI feedback loop VOLUME but hasn't gotten rid of it. The sustain pedal trigering a note in the first place still remains the unsolved problem. Any ideas?