Yamaha QY 300 Owner's Manual page 76

It's sometimes easier to
set a slow tempo for
realtime recording, so you
have plenty of time to enter pattern
and chord changes.
66
Select the Starting Style, Section, Chord, & Tempo
Move the cursor to the style number, section, chord, and tempo parameters,
and set as required.
Engage the Record Ready Mode
Press the key to engage the record ready mode. The red LED above the
key will light.
Select the Realtime Record Mode
Press the [F4] function key ("REAL") to select the realtime record mode.
Record
Press the key to begin recording pattern changes. The metronome will
sound and you'll be given a two-measure count-in prior to the first measure
actually recorded. The count-in is also indicated by negative numbers in the
"Meas" parameter. If a 4/4 pattern is selected, for example, the count-in will
run from measure "-08" to "-01", then recording will begin from measure
"001".
Since you selected "Pat" recording, the cursor will automatically move to
the style number when you start recording. All you have to do to record style
and section changes is to select the required style numbers by using any data
entry method, and section changes via the appropriate micro-keyboard keys.
Remember that all style and section changes occur from the top of the next
measure after the change is entered. Also keep in mind that the INTRO will
automatically switch to the MAIN A pattern, FILL AB will automatically
switch to the MAIN B pattern, and FILL BA will automatically switch to the
MAIN A pattern.