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MIDI Troubleshooting

Got a problem with your MIDI setup? Ian Waugh lists the Top Five MIDI problems and explains how to fix them.

1. No sound

You plug everything in, hit play on your sequencer or some keys on your keyboard and - nothing! The most common causes of this problem are the simplest - is the output connected to an amp and speakers? Is everything turned on?

On the PC, if using a sound card, open the mixer (most sound card software includes a mixer application) and make sure the output is not muted and the volume is turned up.

If all this is as it should be, the next thing to check are the cables - MIDI and audio. Try direct connections. If a sound module is not responding, connect it directly to a MIDI keyboard (without routing it through the computer system).

Make sure the sound card or MIDI interface are correctly installed and connected to the sound module/keyboard/serial port or otherwise able to interface with the outside world.

Specialist interfaces usually require specialist drivers so make sure they are correctly installed. On the PC open the Control Panel>Multimedia>Devices tab, expand MIDI Devices and Instruments and make sure the driver is there.

On the Mac, if you are using Apple's MIDI Manger, OMS or FreeMIDI, make sure it is correctly installed and set-up. Setting up OMS, for example, can be a little involved so read the manual carefully.

2. MIDI drone

Most users will have experienced the dreaded MIDI drone - a stuck note which switches on but doesn't switch off. It happens when a synth receives a Note On message but doesn't received a corresponding Note Off message. It can happen for a number of reasons.

•  If a synth receives more data than it can process - a situation commonly referred to as MIDI Clog or Choke - some instructions may be lost. If it's a Note Off message, a stuck note will result. If this is a repeatable problem with a synth, you're feeding it too much data. If there is a lot of Controller data at the stuck note point, try thinning it down. Most sequencers have a function to do his.

•  Variations on the above include trying to transmit more data than MIDI is capable of handling. The situation can often be eased by using an additional MIDI interface or a MIDI Thru box instead of daisy chaining instruments.

•  If you change MIDI channels during playback an instrument could receive a Note On message on one channel but then the channel is changed before the Note Off message is sent. Check your MIDI tracks for channel hopping.

Many sequencers have a Reset Devices command which will stop the drone but if it persists it needs to be cured at its source.

3. Double notes

If you hear double notes when playing your MIDI keyboard, a little like slapback echo or flanging, the chances are that MIDI Thru in your sequencer and Local Control on your keyboard are not set up correctly. This causes the keyboard to sound two notes - the one you play on the keyboard and another being echoed from the computer.

When MIDI Thru is enabled in a sequencer, it transmits incoming MIDI data back through the MIDI Out socket. Most sequencers transmit this on the MIDI channel of the currently-selected track. You would assign different MIDI channels to different tracks so to play the sound on any particular channel you simply select the track rather than having to physically change settings on the keyboard.

However, this will cause double notes. On your keyboard you need to switch Local Control to Off. This disconnects the keys from the sound circuitry so sounds can only be played via messages arriving at its MIDI In.

4. Volume drops suddenly

This is a surprisingly common occurrence among Cubase users in particular but it can happen with other sequencers, too. Cubase has a section to the left of the tracks called the Inspector where you can set parameters such as pan, transpose and volume for each track. If you take the volume setting down to a low value, say down to 0, the value is transmitted to the MIDI instrument and consequently all subsequent notes play at zero volume.

Solutions include resetting the synth or sound module, inserting a starting volume in the MIDI data or setting the Volume parameters in the Inspector to 127.

5. Weird pitch bend

You load a MIDI file that uses pitch bend and the pitch bend sounds either totally OTT or is non-existent. This can happen when the pitch bend range of the recording instrument is different to that of the receiving instrument. Most instruments have a facility for setting their pitch bend range. A common setting is one octave but some may default to two semitones.

If you dig around inside your synth's settings you should find a parameter which lets you set the pitch bend range. You can probably also set this via MIDI messages.

If you have a GM instrument, the following list of data can be entered in the editor to set the pitch bend range:

Controller 101   0      RPN MSB

Controller 100   0      RPN LSB

Controller   6  12      Set pitch bend to 12 semitones

Controller 101 127      RPN MSB

Controller 100 127      RPN LSB

You can vary the middle value to change the pitch bend range.