What is Latency?
*   In general, the period of time that one component in a system is spinning
    its wheels waiting for another component. Latency, therefore, is wasted 
    time. For example, in accessing data on a disk, latency is defined as the
    time it takes to position the proper sector under the read/write head. 

*   In networking, the amount of time it takes a packet to travel from source
    to destination. Together, latency and bandwidth define the speed and 
    capacity of a network.

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Some considerations:
    If the app is sending 20 ms of audio to the hardware, it must queue 
    another buffer of audio to the hardware before the first is completed.
    If it does not, then audible gapping occurs. This is the latency that 
    bothers users. 

    If an app uses 1 sec buffers, then all "real time" changes can only 
    occur at best in 1 sec increments - i.e. slide the volume and the change
    will take 1 sec. (1 sec is extreme, I know.)  With very complex real-time
    audio manipulation, the amount of buffering that has to take place can be
    extreme.  A poorly written driver could easily hose things, while you 
    would think that the Application is the culprit.

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Modern Sound Cards do not have a Hardware MIDI Synthesizer on board any more.
Therefore, for lack of a Hardware Synth, by default the "MS GS Wavetable SW 
Synth" or "MIDI Mapper" are used, which are OK for MIDI file playback purposes
but have the known Latency issue when using external Keyboards. 

Technology is moving away from MIDI, as Digital Audio and other formats such
as MP3 etc. are prevailing on the market.  Current Sound Cards (unless you go
for Semi-Pro and Pro level at a few hundred $$$) are not complimentary for 
MIDI and issues such as Latency, poor quality etc. are present due to the 
Software Synth.

The good news is that external MIDI Modules have become affordable, providing
better quality sound and overcoming any Latency issues.

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Q:  I love the program. The only problem is that when I strike a key on the
    keyboard, there is a delay to when I hear the note in my headphones.  
    Is there a way to set latency or do you think it is another problem?  
    Please help.


A:  There is no Latency in the transfer rate of the USB MIDI Cable. After all,
    the data being transferred is MIDI (which is not Digital Data that 
    requires a lot of space as well as bandwidth). 
    
    If you are receiving delayed MIDI sound, this is probably due to the 
    fact that a Soft Synth driver is being used for MIDI Output such as
    the "MS GS Wavetable SW Synth" or "MIDI Mapper".

    A software synth works by taking control of a sound card's audio 
    components to create a virtual synthesizer. This greatly slows things 
    down and creates a delay between the time you press a key on your musical
    keyboard until you hear the sound come out of your computer speakers.
  
    To try to alleviate this, try choosing a different soundcard MIDI 
    output driver from within the software: 

    In the application, click on Options > MIDI Port Setup. For 'MIDI Output' 
    you will probably see 'MIDI Mapper'. Click on the words ' MIDI Mapper' 
    and you will get a dropdown box with other options. Make sure you are 
    seeing all of your options by using the up and down arrow keys on your
    computer keyboard. Try selecting each option that appears until you are
    able to hear sound that is not delayed.

See also: 'Syncing / Latency problems'

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