Effect 01/02xy (pitch slide up/down)

Basically, 01xy and 02xy are used to respectively raise or lower the pitch of a note.

You can use these commands on a track command column, whereever there are one or more playing notes, to change their pitch.

The range for xy values is 00..FF (which is equal to 00..255 in decimal base).

The more is xy value, the more the change will be sudden.

Ok, let’see exactly how much do these commands change the pitch of a note.

Firstly, we have to consider how these commands work: they add a number of Hertz (Hz) to the frequency of a note, which basically is an integer mutiple of a fixed integer number, and they add this number at each tick.

If you are familiar with note frequencies, you may have already understood that such a behaviour means that the effect of 01xy and 02xy commands changes based on the note you want to pitch.

The reason for this is quite straightforward: the frequency of a note doubles at each octave, so C-4 (note C of the 4th octave) has half of the frequency of C-5 and double of the frequency of C-3.

The difference in frequency between two adjacent tones (f.e.: C and D) then varies according to the octave:

while A-4 is 440Hz and B-4 is 493Hz (thus a difference of 53Hz),

A-5 is 880Hz and B-5 is 986Hz (thus a doubled difference of 106Hz),

so you need twice the value of xy to gain the same effect in the fifth octave then what you needed in the fourth!

each unit in 01/02xx commands value raises/lowers pitch of 1/594th tone for each tick, AT NOTE C-4.

If you are at speed 06 (F106), put a C-4 note at row 00 and put a set of 0103 from row 00 to 1F, you obtain exact D-4 at row 20, and this result is not dependent on BPM.

Something like this is described above:

so you have this values:

a] 3 units (0103)

b] 6 ticks per row (F106)

c] 33 rows (00..20)

a*b*c = 3*6*33=594

of course, if you need a less/more immediate pitch change, you can change the unit value (010x or 020x), or change the number of ticks per row (F10x); this second option will also alter the speed of flowing of the song.

You can also use glide to note command (05xy?) which works in a similar way, but raises/lowers the pitch until the desired new note is reached.

in the above case:

as I’ve said above, and this can really surprise, this is true only at note C-4: if for example you try this raising the pitch from C-5 to D-5, you will need 0106 or F10C. This is because the pitch commands add the same number of Hertz to the pitch, independently of the present frequency, which becomes twice as high at each octave, and so the difference of frequency between each tone does (i.e.: the difference in Hertz between D-5 and C-5 is quite like the double of the difference between D-4 and C-4).