One note different

Overrides: a repeat that changes one item

% A strain that comes back with one note changed is the oldest form in
% music: play it through, play it again, finish it differently. The body
% stays ONE fixed sequence and the change sits with the statement that
% varies: '\7 1' replaces item 7 of what Strain plays. The index is
% ZERO-BASED, so item 7 is the eighth note and the last one: b3 steps
% down to d4 the first time and rises to c4 the second, which is the
% whole difference between a phrase that waits and a phrase that ends.
 
bpm 96
instrument plain
meter 4
unit 1/4
key c4 maj
 
Strain ::= 1 3 5 3 4 2 .7 2
Closed ::= Strain \7 1
 
assert Strain == c4 e4 g4 e4 f4 d4 b3 d4
assert Closed == c4 e4 g4 e4 f4 d4 b3 c4
assert Strain \0 5 == 5 3 5 3 4 2 .7 2
 
Strain
Closed
 
 
% The index counts what the reference PLAYS, not the tokens in its body.
% Written as two halves the strain plays the same eight notes, and item 4
% is still the f4 that opens the second half. The name Fall standing in
% the way is not an item and does not shift the numbering. That is what
% makes an override durable: a later pass can factor a body into names of
% its own without moving anything an override points at.
 
Rise ::= 1 3 5 3
Fall ::= 4 2 .7 2
Both ::= Rise Fall
 
assert Both == Strain
assert Both \4 5 == 1 3 5 3 5 2 .7 2
assert Both \7 1 == Closed
 
Both \7 1
 
 
% A replacement is ONE element, and to carry marks of its own it has to
% be BRACED: a bare mark after the replacement reads as the reference's
% and covers the whole expansion instead. So 'Strain \7 {1 _4}' holds
% just the last note for four units, while 'Strain \7 1 _4' stretches
% all eight of them. Both are legal, and they are different pieces of
% music.
 
assert Strain \7 {1 _4} == c4 e4 g4 e4 f4 d4 b3 {c4 _4}
assert Strain \7 1 _4 == {Closed}_4
 
Strain \7 {1 _4}
 
 
% An override must come BEFORE any mark, and putting it after fails
% SILENTLY: 'Strain@2 \7 1' neither transposes nor overrides. It plays
% bare Strain, note for note, and reports nothing. The form that works
% puts the override inside what the mark covers, so brace it and mark the
% brace. '{Strain \7 1}@2' is the closed ending a whole tone up, every
% note moved and the replaced one moved with them.
 
assert {Strain \7 1}@2 == {Closed}@2
assert {Strain \7 1}@2 == d4 f#4 a4 f#4 g4 e4 c#4 d4
 
{Strain \7 1}@2
 
 
% One more override and the strain leans on its own dominant: '\4 4#'
% raises the f4 to f#4, and over the d2 in the bass that turns the
% supertonic MINOR into D major, the dominant of the G the phrase is
% walking toward. Four statements over one bass, open and closed and
% sharpened and both, and the bass never moves, because nothing about the
% harmony does. One item changed each time.
 
Sharp ::= Strain \4 4#
Bass  ::= ..1 _2 ..5 _2 ..2 _2 ..5 _2
 
assert Sharp == c4 e4 g4 e4 f#4 d4 b3 d4
assert Sharp \7 1 == c4 e4 g4 e4 f#4 d4 b3 c4
assert Bass == c2 _2 g2 _2 d2 _2 g2 _2
assert 2Dia == {d4, f4, a4}
assert 2Maj == {d4, f#4, a4}
 
{Strain, Bass}
{Closed, Bass}
{Sharp, Bass}
{Sharp \7 1, Bass}

% A strain that comes back with one note changed is the oldest form in
% music: play it through, play it again, finish it differently. The body
% stays ONE fixed sequence and the change sits with the statement that
% varies: '\7 1' replaces item 7 of what Strain plays. The index is
% ZERO-BASED, so item 7 is the eighth note and the last one: b3 steps
% down to d4 the first time and rises to c4 the second, which is the
% whole difference between a phrase that waits and a phrase that ends.

bpm 96
instrument plain
meter 4
unit 1/4
key c4 maj

Strain ::= 1 3 5 3 4 2 .7 2
Closed ::= Strain \7 1

assert Strain == c4 e4 g4 e4 f4 d4 b3 d4
assert Closed == c4 e4 g4 e4 f4 d4 b3 c4
assert Strain \0 5 == 5 3 5 3 4 2 .7 2

Strain
Closed

% The index counts what the reference PLAYS, not the tokens in its body.
% Written as two halves the strain plays the same eight notes, and item 4
% is still the f4 that opens the second half. The name Fall standing in
% the way is not an item and does not shift the numbering. That is what
% makes an override durable: a later pass can factor a body into names of
% its own without moving anything an override points at.

Rise ::= 1 3 5 3
Fall ::= 4 2 .7 2
Both ::= Rise Fall

assert Both == Strain
assert Both \4 5 == 1 3 5 3 5 2 .7 2
assert Both \7 1 == Closed

Both \7 1

% A replacement is ONE element, and to carry marks of its own it has to
% be BRACED: a bare mark after the replacement reads as the reference's
% and covers the whole expansion instead. So 'Strain \7 {1 _4}' holds
% just the last note for four units, while 'Strain \7 1 _4' stretches
% all eight of them. Both are legal, and they are different pieces of
% music.

assert Strain \7 {1 _4} == c4 e4 g4 e4 f4 d4 b3 {c4 _4}
assert Strain \7 1 _4 == {Closed}_4

Strain \7 {1 _4}

% An override must come BEFORE any mark, and putting it after fails
% SILENTLY: 'Strain@2 \7 1' neither transposes nor overrides. It plays
% bare Strain, note for note, and reports nothing. The form that works
% puts the override inside what the mark covers, so brace it and mark the
% brace. '{Strain \7 1}@2' is the closed ending a whole tone up, every
% note moved and the replaced one moved with them.

assert {Strain \7 1}@2 == {Closed}@2
assert {Strain \7 1}@2 == d4 f#4 a4 f#4 g4 e4 c#4 d4

{Strain \7 1}@2

% One more override and the strain leans on its own dominant: '\4 4#'
% raises the f4 to f#4, and over the d2 in the bass that turns the
% supertonic MINOR into D major, the dominant of the G the phrase is
% walking toward. Four statements over one bass, open and closed and
% sharpened and both, and the bass never moves, because nothing about the
% harmony does. One item changed each time.

Sharp ::= Strain \4 4#
Bass  ::= ..1 _2 ..5 _2 ..2 _2 ..5 _2

assert Sharp == c4 e4 g4 e4 f#4 d4 b3 d4
assert Sharp \7 1 == c4 e4 g4 e4 f#4 d4 b3 c4
assert Bass == c2 _2 g2 _2 d2 _2 g2 _2
assert 2Dia == {d4, f4, a4}
assert 2Maj == {d4, f#4, a4}

{Strain, Bass}
{Closed, Bass}
{Sharp, Bass}
{Sharp \7 1, Bass}

running…edit it and it re-runs as you type

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