The frequency or "pitch" of this sound can be changed by adding a pitch value after the BELL command, ranging from 1 for a very deep ring, up to 96 for an ultra high pitched sound. You can hear the range of frequencies with this example:
E> For F=1 To 96
Bell F : Wait F/10+1 : Rem Vary delay
Next F
Musical pitch
The values from 1 to 96 that are used to control the pitch of the BELL sound correspond to the
notes on the keyboard of a piano. The white key at the extreme left-hand side of the keyboard is
known as Bottom C, and corresponds to pitch value 1. Value 2 is the equivalent to the black note
next to it, which is a C#, and so on up to "Middle C" at pitch value 37, then all the way up to 96.
Grand piano keyboards run out of notes after 88, and most synthesizer keyboards have a lot less
than that.
In Western music, notes are given their own code letter so that musicians can all refer to the same pitch when they try and play together. These letters repeat themselves after twelve notes, and each group of twelve is known as an "octave".
Here is a table of pitch values, along with their musical note equivalents and octave groupings.
Octave
Note 0 1 2 3 4 5 6 7
C 1 13 25 37 49 61 73 85
C# 2 14 26 38 50 62 74 86
D 3 15 27 39 51 63 75 87
D# 4 16 28 40 52 64 76 88
E 5 17 29 41 53 65 77 89
F 6 18 30 42 54 66 78 90
F# 7 19 31 43 55 67 79 91
G 8 20 32 44 56 68 80 92
G# 9 21 33 45 57 69 81 93
A 10 22 34 46 58 70 82 94
A# 11 23 35 47 59 71 83 95
B 12 24 36 48 60 72 84 96
Channels and voices
The Amiga produces sound like a river, and AMOS Professional allows you to split this river
into four separate channels, all pouring out at the same time, but each capable of individual
control. These channels can be heard individually, or mixed together, or directed to the left and
right creating stereo sound. They can also be individually increased and decreased in volume, or
dammed up altogether.
Each of these channels can be given a different "voice", and each voice can be controlled in terms of volume and direction.