Default Register Definitions

ORCH-9C) creates the following default registers when used on a Model III TRS-80:

JASEFA50000E JBS48F80000F JCSE0500000A JDSF4080000B JES4F280000D

If you are satisfied with the sound produced by these instrument registers, there is no need to type them into the file. The compiler automatically uses them during a "SCORE". Just use the "Y" command to assign the register name (A, B, C, D, or E) to any voice.

The "J" command is primarily used for CHANGING the sound or volume of the default instrument registers, allowing each music file to contain a different set of register definitions.

Note that partials 5-8 are not defined in the default registers (they are set to 0). In general, you should not define more than the first four partials if you use ORCH-90 on a Model III TRS-80 (and you should only select the 3 or 4-voice option, not 5-voice). Defining additional partials could cause some undesirable "aliasing". This effect can be reduced somewhat by transposing the piece down with the "<" command. However, if a register is ONLY used to play low bass notes, some additional partials may be added without creating aliasing. It's easy to experiment with the partials. Just go into the EDIT mode, add additional partials (or change the strength of the existing partials), then SCORE and PLAY.

When used on a Model 4 or 4P TRS-80, the ORCH-90 takes advantage of the faster (4 Mhz) clock speed and defines an extra two partials in some of the registers. These are the default register values on a Model 4 or 4P:

JASEFA54E00E JBS48F8F200F JCSE050F000A JDSF4080000B JES4F281400D

The faster clock speed of a Model 4 or 4P also allows you to define extra partials. You'll be able to define all the partials (1-8) without aliasing, unless you are trying to play very high notes. Really high pitch notes are obtained by using registers with fewer defined partials. For example, the default D register on a Model 4 can play higher notes than any of the other registers because it has only the first four partials defined. On a Model III, the default C register can play the highest notes because it has only the first three partials defined.

Since partials are actually tones themselves, you can single them out and listen to them individually. For example, try these short files (separately) on a Model 4:


V1YA P01


}V1 YA P01


V1YA P01

define only partial #1 in register A

assign register A to Voice 1 Part 01

plays a scale from Middle-C to ONE octave above Middle-C

define only partial #2 in register A

assign register A to Voice 1 Part 01

plays a scale from ONE octave above Middle-C to TWO octaves above Middle-C

define only partial #4 in register A

assign register A to Voice 1 Part 01

plays a scale from TWO octave above Middle-C to THREE octaves above Middle-C

In Example 1 we use only the fundamental tone (partial #1), so ORCH-90 plays the correct notes fFom Middle-C to one octave above Middle-C.

In Example 2 we eliminate partial #1 and use only partial #2. Partial #2 is twice the frequency of partial #1, therefore the same scale sounds an octave higher than normal.

In Example 3 we eliminate partial #2 and use only partial #4. Partial #4 is four times the frequency of partial #1, therefore it sounds TWO octaves higher than the original scale.

Note that we skipped the 3rd partial. This partial is not an octave multiple of the fundamental tone, so the resulting scale would not be exactly one or two octaves higher. Try it yourself if you're curious.

This demonstrates the individual sounds of various partials, but music played using only single-partial tones is not very interesting (or realistic). No real musical instruments (except ORCH-90 and some other synthesizers) are capable of producing such single-partial tones. All other instruments create multiple-harmonic sounds. In fact, that's what makes them unique. Even an instrument as simple as a kazoo produces several harmonics. ORCH-90's best instrumental effects are obtained using registers with combinations of partials.

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