[0001] This patent application for an industrial invention concerns a machine, capable of
automatically and simultaneously reproducing one or more notes between which there
is a pre-set frequency interval, set and taken from look-up tables containing all
musically correct harmonies that can be matched with any note, played or sung, within
the scope of the chord and type of chord chosen
[0002] The machine according to the invention is designed to be used by musicians that
play monophonic instruments, i.e. instruments capable of emitting just one note at
a time, thus rendering it impossible to superimpose over this note a musical harmony,
in other words a combination of different notes, the formation of which can be different
each time, even though the same note is played, depending on the chord chosen by the
musician.
[0003] The machine according to the invention is also designed to be used by singers in
that the human voice is the equivalent of a monophonic instrument.
[0004] Having said the above, it should be remembered that each time a played or sung note
is to be accompanied by a harmony, the solution always adopted is that of putting
the musician alongside an orchestra and the singer together with a backing group.
[0005] Recently, the most advanced technology in the musical sector has proposed a machine,
a so-called "harmonizer", capable of reproducing starting from a played or sung note
and depending on the chord chosen, a harmony with intervals or a set frequency between
each note, wherein this frequency can only be altered by acting manually on switches
provided for this purpose.
[0006] This machine, without doubt valid if the performer always stays on the same chord
and the same guide-note, immediately becomes ineffective as soon as the guide-note
or the chosen chord are changed.
[0007] In fact, as long as the chord remains the same, the harmony emitted by the harmonizer
is musically correct only for some of the notes of the scale, as can be seen from
the chart that follows, wherein notes and harmonies are indicated with conventional
international symbols that are used and recognised.

[0008] In the above example, less than 50% of the notes in the scale can be used in the
"C" chord and only three ( G,F,C,) can be considered musically correct in the harmony
reproduced by the harmonizer.
[0009] If the "C" chord is modified to minor, seventh, diminished, raised etc., to be able
to have notes in musically correct harmony, it would be necessary to use at least
five switches, corresponding to the following pre-selected frequency intervals between
the notes which make up the harmony : third minor ( 3 semitones), third major ( 4
semitones), fourth ( 5 semitones), fourth major ( 6 semitones) fifth ( 7 semitones).
[0010] In the chart which follows, it is made clear how in the same "C" chord, should there
be the desire to combine a musically correct harmony with the notes in the scale,
it is necessary to resort to at least five different frequency intervals.

[0011] Moreover, it should be said that many musicians or singers are not able to think
of the correct frequency interval for the harmony to be associated with the note played
or sung, due to the fact that during the performance of a piece, they have to simultaneously
bear in mind the following factors :-
- chord used, type of chord, guide-note, position of guide note in the scale, use
of pre-selection switches for pre-set frequency intervals. The aim of the instant
invention is to overcome the abovementioned limitations, characteristic of the type
of harmonizer currently known and in use, by proposing a new machine for the reproduction
of sound, which, starting from the guide note and according to the chord and type
of chord pre-selected, is able to produce a harmony which is always musically correct
made up of notes separated by a pre-established frequency interval, which can be read
on special reference tables, which contain in memory all the harmonies which can be
correctly associated with any note in the scale, according to a given chord and type
of chord.
[0012] As is known to those involved in the field of music, the background chords can be
inserted by the performer of the piece of music, by means of a pedal keyboard or keyboard;
as far as the pedal keyboard and also the keyboard are concerned, the type of chord
can be pre-selected, if only one key is pressed by using one pedal, normally known
as " chord switches" with four switches, the type of chord being selected by the combination
of these switches.
[0013] The machine according to the invention essentially works as follows :
When a note is inserted through a microphone, by means of a well-known electronic
circuit, called "ADC" ( analog to digital converter), this note is transformed to
a digital code which can be processed by a microcomputer and memorised so that it
can be subsequently reproduced. By means of a special circuit, the frequency of the
played or sung note, is registered and calculated; according to the value of this
frequency the correct harmony to accompany the note being entered is automatically
found on a table containing memorized data which are used for each note in the scale
to obtain a correct musical harmony for each type of chord within the same key.
[0014] In other words, the memorised data is pre-selected from the table according to the
note being entered and according to the name and type of chord pre-established each
time by the performer of the piece.
[0015] From the reading of the table, the frequency intervals can be obtained which are
necessary to find the correct harmony to be associated with the played or sung guide-note
and the value of the intervals indicated determines the frequencies of reproduction
of the digital recording carried out.
[0016] For further clarity of explanation, the description of the machine according to
the invention, continues with reference to the attached drawings, reproduced for illustrative
and not restrictive purposes, in which :-
-Fig.1 is a functional block diagram of the machine according to the invention.
Block 1 ( Preamp ), comprises a phase of amplification and impedance adaptation for
the various inputs ( microphone, line,balanced input for microphone ).
Block 2 ( lowpass filter ), comprises a lowpass filter with a slope of at least 24
db. per eigth.
Block 3 (S/H), consists of a sample and hold circuit, which is able to maintain the
signal stable for long enough to allow block 4 to make the analog to digital conversion.
Block 4 ( ADC) comprises an analog to digital converter, which converts the analog
signal to digital codes.
Block 5 ( Pitch detector) consists of a special circuit made up of an adaptive filter
and signal compressors; this circuit will extract the basic frequency and send a series
of impulses to the micro-processor (block 14), from which the timing of the signal
being entered will be determined by means of a counter.
Block 6 (H.S. Micro) comprises a high speed micro-processor, this processor is used
to read the data in RAM ( Block 7), at varying speeds according to the information
supplied by the tables contained in Block 14; it also controls the multiplexer ( Block
9)
Block 7 (RAM) consists of a 16-bit memory bank where the ADC data are memorised (
Block 4)
Block 8 (DAC) consists of a digital to analog converter able to reconstruct the analog
signal from digital codes.
Block 9 ( MPX) comprises a multiplexer circuit which allows the output of two or more
signals, using only one DAC.
Block 10 ( S/H) consists of a sample and hold circuit which allows the stabliizing
of the signal during the switching time of the multiplexer.
Block 11 (lowpass filter) consists of a lowpass filter with a slope of at least 24
db. per eigth.
Block 12 ( Midi I.O.T ) comprises standard MIDI inputs and outputs, where devices
equipped with MIDI interface can be connected, to control or be controlled by the
machine according to the invention.
Block 13 ( Pedal ) comprises a pedal keyboard with at least 13 notes, which is used
to select the chord note.
Block 14 ( Micro look-up table) consists of a micro-processor which reads the tables
and sends the information concerning the notes to be reproduced to the rapid microprocessor
(Block 6), on the basis of information obtained from the controls ( 18), the pedal
(13), the chord switches (17), the MIDI (12) and the pitch detector (5).
Block 15 ( Mixer) consists of various pre-amplifiers and a mixer with various volume
controls for each sound being emitted.
Block 16 ( OUT) comprises various output sockets which will allow the connection of
the machine to the power amplifier line.
Block 17 ( Chord switches) consists of a pedal with 4 switches, which, combined, allow
the selection of the type of chord.
Block 18 ( Commands) consists of various controls which allow the selection of the
various functions and a display which will indicate the function selected.
[0017] With reference to Fig.1, it can be observed that the played or sung note which has
been amplified and filtered by blocks (1) & (2), is sent both to Block (3), where
it is temporarily memorised to serve block (4), and to block (5), which extracts the
basic frequency of the entering signal and sends it to block (14), where the musically
correct intervals for each musical note, each chord and each type of chord are memorised
so as to create the harmony.
[0018] Block (4) converts the analog signal to a digital code and all the digital codes
are registered on block (7) and at the same time, sent to block (6), which is able
to read all the data as it is being registered and memorised in block (7) with varying
frequencies, in compliance with the indications supplied by block (14), the data emerging
therefrom being obtained from that memorised in the table and selected and read each
time according to frequency indicated by block (5), the chord indicated by block (13)
and the type of chord indicated by block (17).
[0019] The data recorded in block (7) and reproduced by block (6) with the correct frequencies
established by block (14) is re-converted from digital to analog by block (8) to
then be sent to the 'OUT' block (16), by means of processing of the type normally
in use, which is activated by the series of blocks (9), (10),(11) and (15).
[0020] It should be noted, that block (14) is also equipped to calculate the difference
between the frequency of the guide-note being entered which is measured by block (5)
and the basic frequency, the value measured by block (5) being within the tolerance
range of the aforesaid basic frequency.
[0021] In this way, by means of a function selector key, block (14) automatically works
out an algebraic sum between the calculated difference and the reproduction frequency
so that the notes which make up the harmony reproduced by block (6) are in tune with
the note memorised and preselected in the block (14) table, in spite of the fact
that the guide note being entered in block (1) has a different frequency to the aforementioned
memorized noted.
[0022] In conclusion, this means that perfect harmonies are always obtained even if the
note entered is slightly out of tune.
1. Automatic machine for the simultaneous reproduction of several notes with musical
frequency intervals pre-set on and provided by look-up tables, containing all the
harmonies for each note, according to the chord and type of chord chose, characterised
by the fact that it comprises a memory (Block 14), where for each note, each chord
and each type of chord the frequency intervals which must exist between the notes
of a musically correct harmony and the guide-note entering the machine are memorised,
said guide-note being amplified and filtered, its frequency being identified by block
(5), converted to digital code ( by block (4) ) and recorded in a memory ( Block 7),
so that it can be reproduced subsequently by block (6), with the frequency intervals
supplied by block (14), the memorized data thereof being selected each time according
to the frequency of the guide-note being entered ( this information being supplied
by block (5) ), to the pre-selected chord ( this information being supplied by block
(13)) and to the type of chord pre-selected ( this information being supplied by
block (17));
2) Automatic machine for the simultaneous reproduction of several notes with musical
frequency intervals pre-set on and provided by look-up tables, containing all the
harmonies for each note, according to the chord and type of chord chose, according
to claim 1), characterised by the fact that block (14) is capable of measuring the
difference between the frequency of the guide-note being entered ( measured by block
(5)), and the basic frequency, the value measured by block(5) coming within the tolerance
range of the aforesaid basic frequency, and is capable of working out the algebraic
sum of the difference calculated and the reproduction frequency.