Alesis A6 User Manual

 A tempo source (such as a sequencer) emits 24 timing messages

(clocks) per quarter note. Each device synchronized to the sequencer advances by
1/24th of a quarter note when it receives the clock message, thus keeping units in
sync after they’ve both started at the same time. Many devices subdivide this clock
signal internally for higher resolution (e.g., 96 pulses per quarter note).

 Signals all rhythmically-based units when to start playing.

 Signals all rhythmically-based units when to stop playing.

 Unlike a Start command which re-starts a sequencer or drum machine

from the beginning of a song each time it occurs, sending a Continue message after a
Stop command will re-start units from where they were when they stopped.

. Active Sensing is a precautionary measure in MIDI that allows all

instruments in a MIDI system to turn off any playing voices in the event that one or
more MIDI cables become unplugged. Because receiving instruments wait for a Note
Off command to know when a note or chord has stopped playing, yanking a MIDI
cable out while notes are being played will cause receiving instruments to have any
sustaining notes get “stuck on”.

With Active Sensing, a message is sent from the transmitting device to all receiving
devices about three times a second. Once receiving devices recognize this message,
they will expect to continue to receive it. If this message stops – using our example of
a MIDI cable being accidentally pulled out – the receiving instruments will perform
an All Notes Off to stop any voices that might be playing at the time. When the
offending cable is found and replaced, the system returns to normal.

. Every MIDI instrument and device has a default set of parameters (all

the factory settings the unit had when you first took it out of the box). These defaults
can be restored if you manually initialize the instrument (see Troubleshooting
section). System Reset is the command used to accomplish this via MIDI.

 This indicates how many “MIDI beats” (normally a 16th note)

have elapsed since a piece started (up to 16,384 total beats or 1,024 measures in 4/4).
It is primarily used to allow different sequencers and drum machines to auto-locate
to each other. If you start your sequencer for example, the other devices will
automatically jump to the same place in the song, whereupon all continue on
together. The sequencer in the A6 does not respond to SPP.

. Intended for clock-based devices (such as drum machines and

sequencers), this message tells all units in the system which Song Number to select.
This handy function allows you to instruct all clock-based units in your MIDI rig to
load the appropiate song data from their own internal memory remotely.

You can think of Song Select as a kind of a Program Change command for drum
machines and sequencers, although Song Select commands are not channelized. In
fact, drum machines and sequencers do have the ability to respond to Program
Change commands transmitted on a specific Channel. When they do, they recall an
individual drum pattern or sequence. Song Select is used to recall a Song which is
typically composed of many patterns or sequences in the form of a finished song.

. Primarily intended for analog synthesizers which need to have their

oscillators tuned periodically, this command instructs all units in the system to
initiate an autotune routine.