Index modulation picks a note from the current scale or chord. Only note tracks support index modulation. If a chord exists, the index accesses the chord's tones, otherwise if a scale exists, the index accesses the scale's tones. If neither exists, index modulation has no effect. If a track has multiple unmuted index modulators, they're summed to produce a single index value.
The index is zero-based, meaning zero accesses the first tone, one accesses the second tone, and so on. If the index exceeds the range of the chord or scale, it wraps around. For example, if the scale has seven tones, they correspond to index values 0 through 6. If the index has a value of 7, it wraps around and accesses the first tone. Similarly, if the index has a value of −1, it wraps around in the other direction and accesses the last tone.
The mapping from index values to scale or chord tones may be affected by the order in which the scale or chord modulations are listed for the target track. For this reason, it's advisable to keep scale and chord modulations in ascending sequential order.
Duplicate notes
A duplicate note occurs when an instrument plays the same MIDI note value twice in a row. Duplicate notes may be perceived as flaws, especially in arpeggios. If you're using index modulation to pick scale or chord tones, you have the option to prevent duplicate notes automatically, by picking the tones in a slightly different order.
Prevention adds a retry to the indexing. The picked tone is compared to the relevant channel's previous note, and if they match, the index value is incremented by one, and the indexing is then retried. This prevents a duplicate note provided 1) the scale or chord contains at least two tones, and 2) all tones in the scale or chord are unique.
Duplicate note prevention is enabled on a per-channel basis, via the Duplicates column in the channels bar. To prevent duplicate notes, change the relevant channel's drop list value from "Allow" to "Prevent". Prevention can also be controlled via MIDI mapping or an internal controller.