The MIDI keyboard produces no sound when you do not plug in the audio and MIDI cables tightly or install them incorrectly. Keyboard channels that you set to "off" will not produce any sound. A low setting on the keyboard volume control or a muted mixer setting can also prevent sound from coming through your keyboard speakers. Corrupt MIDI software drivers can prevent MIDI files from playing at all.
The MIDI keyboard will produce a droning noise when a note becomes stuck and you can't turn it off even when you release the key when the MIDI Thru function is on in the computer. Keep the keyboard's Local Control function on, and check for MIDI channel hopping on your MIDI tracks. Switching channels during track playback or overloading a synthesizer with data can also cause MIDI droning.
Double notes sound on the keyboard when you have not correctly set up the MIDI Thru controlled by a sequencer and Local Control on the keyboard. This causes the keyboard to sound the note you are playing and to echo the note from the sequencer controlled by your computer. Assign Local Control to the keyboard and switch off MIDI Thru on the sequencer to prevent double notes.
Sudden volume drops can occur when you have a track volume on a sequencer set to a low value. The low volume value passes on to the MIDI keyboard, where the tones then play at low or zero volume. Set all of the sequencer track volumes before recording, and perform minimal volume adjustments to prevent subsequent sudden volume drops.
Polyphony defines the maximum number of notes an instrument can play at one time. Dropped notes occur in recorded MIDI tracks when you run out of channel space. Higher priority channels will take up more polyphony space and the synthesizer will drop notes from lesser priority channels in order to sound the next higher priority channel note. Assign instruments that are more important to higher priority channels.
You may have specified pitch bend on a MIDI recording, but the bend sounds strange or does not seem to be applied at all. Recording and playback MIDI instruments may have different pitch bend ranges for the same instruments. The pitch range on the playback MIDI instrument may need adjustment before MIDI track playback.