Range extension
This tutorial describes how to extend the range of an instrument which does not have samples for all notes in the desired range. This is not complicated, but there are some downsides to doing it the simple way. Things work the same way when extending up or down. When there are intermediate pitches missing, for example when an instrument is sampled every minor third or every octave, there won't be much choice, though if round robins are available the last approach can prove useful.
Simple extension of closest available sample
Let's say we have only one sampled violin section with the following map, and we want to be able to play the notes for another octave above the highest currently avaialble note.
<region>sample=c4.wav key=48
<region>sample=db4.wav key=49
<region>sample=d4.wav key=50
<region>sample=eb4.wav key=51
<region>sample=e4.wav key=52
<region>sample=f4.wav key=53
<region>sample=gb4.wav key=54
<region>sample=g4.wav key=55
<region>sample=ab4.wav key=56
<region>sample=a4.wav key=57
<region>sample=bb4.wav key=58
<region>sample=b4.wav key=59
<region>sample=c5.wav key=60
The simplest way is to just stretch the highest note. Using lokey, hikey and pitch_keycenter as separate opcodes is better than using key and transpose, as it allows one region to cover a wide range of pitches.
<region>sample=c5.wav lokey=60 hikey=72 pitch_keycenter=60
Note that ARIA will produce no sound if asked to transpose a sample more than four octaves up - if that is needed, create some extra copies of the samples and transpose them in an audio editor. This accounts for transposition, pitch bend and any other tuning adjustments, so if an octave of pitch bend is needed, the maximum effectively avaialable transpotition becomes an octave less. There is no similar limitation with downward transposition, though.
Filling in missing pitches
In the above case, the range is being stretched upwards, but the same principle applies if there are notes missing within the range, whether due to recording errors, or the limitations of instruments which can't produce all notes of the chromatic scale.
Let's say we have a simple pentatonic xylophone.
<region>sample=c4.wav key=48
<region>sample=d4.wav key=50
<region>sample=f4.wav key=53
<region>sample=g4.wav key=55
<region>sample=a4.wav key=57
<region>sample=c5.wav key=60
<region>sample=d5.wav key=62
<region>sample=f5.wav key=65
<region>sample=g5.wav key=67
<region>sample=a5.wav key=69
<region>sample=c6.wav key=72
This would work similar as above, covering every pitch with the nearest available note. Whether to stretch up or down when there are two equally distant notes available is a judgment call. It might be worth trying both to see which sounds best. The below example goes up and doesn't extend the range beyond the highest or lowest available sample, only fills in the gaps.
<region>sample=c4.wav lokey=48 hikey=49 pitch_keycenter=48
<region>sample=d4.wav lokey=50 hikey=51 pitch_keycenter=50
<region>sample=f4.wav lokey=52 hikey=54 pitch_keycenter=53
<region>sample=g4.wav lokey=55 hikey=56 pitch_keycenter=55
<region>sample=a4.wav lokey=57 hikey=58 pitch_keycenter=57
<region>sample=c5.wav lokey=59 hikey=61 pitch_keycenter=59
<region>sample=d5.wav lokey=62 hikey=63 pitch_keycenter=62
<region>sample=f5.wav lokey=64 hikey=66 pitch_keycenter=65
<region>sample=g5.wav lokey=67 hikey=68 pitch_keycenter=67
<region>sample=a5.wav lokey=69 hikey=70 pitch_keycenter=69
<region>sample=c6.wav lokey=71 hikey=72 pitch_keycenter=72
Alternating several samples
The above is good enough in a lot of cases, though it might become obviously audible that the entire top octave uses the same sample. We could use the top two or three samples instead, and alternate them like this:
<region>sample=c5.wav key=60
<region>sample=bb4.wav lokey=61 hikey=61 pitch_keycenter=58
<region>sample=b4.wav lokey=62 hikey=62 pitch_keycenter=59
<region>sample=c5.wav lokey=63 hikey=63 pitch_keycenter=60
<region>sample=bb4.wav lokey=64 hikey=64 pitch_keycenter=58
<region>sample=b4.wav lokey=65 hikey=65 pitch_keycenter=59
<region>sample=c5.wav lokey=66 hikey=66 pitch_keycenter=60
...and so on, continuing to the highest desired note.
Using different round robins
However, in the above case, notes a minor third apart will still use the same sample, and there's a minor third interval in both minor and major triads. There might not be a good way to get around this with the sample set we have above, but if we have two round robins, we could do something like this:
<group>
seq_length=2
<region>sample=c4_rr1.wav key=48
<region>sample=db4_rr1.wav key=49
<region>sample=d4_rr1.wav key=50
<region>sample=eb4_rr1.wav key=51
<region>sample=e4_rr1.wav key=52
<region>sample=f4_rr1.wav key=53
<region>sample=gb4_rr1.wav key=54
<region>sample=g4_rr1.wav key=55
<region>sample=ab4_rr1.wav key=56
<region>sample=a4_rr1.wav key=57
<region>sample=bb4_rr1.wav key=58
<region>sample=b4_rr1.wav key=59
<region>sample=c5_rr1.wav key=60
<region>sample=bb4_rr2.wav lokey=61 hikey=61 pitch_keycenter=58
<region>sample=b4_rr2.wav lokey=62 hikey=62 pitch_keycenter=59
<region>sample=c5_rr2.wav lokey=63 hikey=63 pitch_keycenter=60
<region>sample=bb4_rr1.wav lokey=64 hikey=64 pitch_keycenter=58
<region>sample=b4_rr1.wav lokey=65 hikey=65 pitch_keycenter=59
<region>sample=c5_rr1.wav lokey=66 hikey=66 pitch_keycenter=60
<region>sample=bb4_rr2.wav lokey=67 hikey=67 pitch_keycenter=58
<region>sample=b4_rr2.wav lokey=68 hikey=68 pitch_keycenter=59
<region>sample=c5_rr2.wav lokey=69 hikey=69 pitch_keycenter=60
<region>sample=bb4_rr1.wav lokey=70 hikey=70 pitch_keycenter=58
<region>sample=b4_rr1.wav lokey=71 hikey=71 pitch_keycenter=59
<region>sample=c5_rr1.wav lokey=72 hikey=72 pitch_keycenter=60
<group>
seq_length=2
seq_position=2
<region>sample=c4_rr2.wav key=48
<region>sample=db4_rr2.wav key=49
<region>sample=d4_rr2.wav key=50
<region>sample=eb4_rr2.wav key=51
<region>sample=e4_rr2.wav key=52
<region>sample=f4_rr2.wav key=53
<region>sample=gb4_rr2.wav key=54
<region>sample=g4_rr2.wav key=55
<region>sample=ab4_rr2.wav key=56
<region>sample=a4_rr2.wav key=57
<region>sample=bb4_rr2.wav key=58
<region>sample=b4_rr2.wav key=59
<region>sample=c5_rr2.wav key=60
<region>sample=bb4_rr1.wav lokey=61 hikey=61 pitch_keycenter=58
<region>sample=b4_rr1.wav lokey=62 hikey=62 pitch_keycenter=59
<region>sample=c5_rr1.wav lokey=63 hikey=63 pitch_keycenter=60
<region>sample=bb4_rr2.wav lokey=64 hikey=64 pitch_keycenter=58
<region>sample=b4_rr2.wav lokey=65 hikey=65 pitch_keycenter=59
<region>sample=c5_rr2.wav lokey=66 hikey=66 pitch_keycenter=60
<region>sample=bb4_rr1.wav lokey=67 hikey=67 pitch_keycenter=58
<region>sample=b4_rr1.wav lokey=68 hikey=68 pitch_keycenter=59
<region>sample=c5_rr1.wav lokey=69 hikey=69 pitch_keycenter=60
<region>sample=bb4_rr2.wav lokey=70 hikey=70 pitch_keycenter=58
<region>sample=b4_rr2.wav lokey=71 hikey=71 pitch_keycenter=59
<region>sample=c5_rr2.wav lokey=72 hikey=72 pitch_keycenter=60
This is obviously much more complicated than the simple version we started with, and the extra complexity might not be worth it in many cases, but if needed things can be done this way.
Recording extra notes
In cases where it's very important to avoid using the same sample too many times, it's possible to start addressing this at the recording stage, and record additional samples of the notes which will need to be stretched. Of course this could be more work than just recording the target pitches in the first place, but if the pitches are difficult to produce consistently (for example are notes that a singer can hit only with considerable strain) or just physically fall outside the range, it may be a viable option.
True legato samples.
Extending the range with true legato samples requires extending the range for both the previous note (the sw_previous values) and the new note (the lokey/hikey values). It is important that when transposing a legato transition sample, not only lokey and hikey must be changed, but lokey, hikey and sw_previous must all be changed by the same value.
Here is a process which has worked in practice for extending the range of a legato instrument upwards by a major second by transposing the samples by a minor third.
- Copy regions with the key to be extended. Add the amount of shift (3 if taking the second-highest and third-lowest note and extending the range by a major second) to sw_previous, lokey and hikey to the copy.
- Copy regions with the sw_previous to be extended (which will include some regions copied in the previous step). Likewise add the amount of shift to sw_previous, lokey and hikey to the copy.
- Delete the regions with sw_previous above the new max range (or could try avoiding copying them in the first step, but this way is probably safer).
- Delete the duplicate regions copied in both of the first two steps.
There will be no legato samples covering the widest intervals from the extended notes to the farthest notes on the other side. If the instrument has legato samples only recorded within a certain range (for example only for intervals up to an octave), this isn't going to create any additional problems that didn't already have to be solved when making the non-extended legato instruments. Often the best choice us defaulting to an octave leap in the correct direction is the best choice, but other possibilities are triggering a regular sustain and even producing no sound at all. If an instrument does have every possible note transition in its range sampled, however (quite possible for instruments with a small range, such as rebab), the nearest available interval is probably the most reasonable choice.