Kevin Doyle
There are three main types of structure available in AMPLE:
a) Loops;
b) Conditionals;
c) Conditional loops.
b) Conditionals;
c) Conditional loops.
I will examine each of these in turn over the next few
issues of AMPLINEX and give examples of their use.
In this issue I will look at loops.
Loops in AMPLE
These are the simplest AMPLE structures and allow a group of
AMPLE words to be performed a defined number of times. E.g.
"loop" [ 8 FOR( 48, 0:CDEFGABC )FOR ]
will play the scale of C eight times in succession. This
technique can be very useful when a musical part contains a repeating riff
which may only change after a certain number of bars. E.g.
"riff" [ 24, -2:GBgC/bg/ ]
"12-bar-blues" [ 0@ 4 FOR( riff )FOR 5@ 2 FOR( riff
)FOR 0@ 2 FOR( riff )FOR -5@ 1 FOR( riff )FOR 5@ 1 FOR( riff )FOR 0@ 2 FOR(
riff )FOR ]
In the above example the lines containing '1 FOR( riff )FOR'
could, of course, have been more succinctly written merely as 'riff'.
FOR(…)FOR loops can be 'nested' to give more complex
structures e.g. -
"riff1" [ 24, -1:CCFe ]
"riff2" [ 24, -1:gABC ]
"riff3" [ 24, -1:DDFe ]
"riff4" [ 24, -1:Gfed ]
"loops" [ 4FOR( 2FOR( 2FOR( riff1 riff2 )FOR 2FOR(
riff3 riff4 )FOR )FOR 2FOR( riff1 riff2 riff3 riff4 )FOR )FOR ]
There are two AMPLE words which are designed specifically
for use within a FOR(…)FOR loop - these are COUNT and INDEX. They both act as
counters - the difference is that COUNT starts at 1 and increments by one
through each pass of the loop. INDEX starts at the number of loops to be
performed and reduces by one until it reaches 1. So,
"upoct" [ 4FOR( 24, INDEX:CDE )FOR ]
will play CDE with octave settings of 4, 3, 2 and 1,
whereas,
"downoct" [ 4FOR( 24, COUNT:CDE )FOR ]
will play CDE with octave settings of 1, 2, 3 and 4.
In the next issue I will be looking at conditional
structures using IF and ELSE and the use of the logical operators ON, OFF, AND,
OR, XOR and NOT.
Published in AMPLINEX 001, September 1987
