Legato Interval Sampling

A simple yet effective method for more natural legato sampling

A conventional approach to sample-based virtual instruments has long been to record individual notes of a given instrument and then play them back, individually. This approach, however, is significantly lacking in authenticity for instruments with continuous pitch, e.g. string instruments. The problem is that with a continuos-pitch instrument the player not only plays the individual notes, but also the transitions in between the notes.

Therefore, when sampling such instruments and aiming for an authentic virtual representation, the transitions should be captured. Doing so is surprisingly straightforward. Firstly, one records pairs of notes in addition to the individual pitches. The magic happens when processing and mapping the samples. The ‘conventional’ single sample of a correct pitch is used for the first note of a legato phrase as per usual, but the rest of the notes in the phrase make use of the sampled pairs. The first note of a pair is discarded, and what remains is the note that is truly and originally sampled from a two-note legato phrase. Thus, when a legato phrase is played on the virtual instrument, the transitions are included in addition to the actual notes.

Obviously, and unfortunately, this approach requires O(n²) samples (and as the sampling process is largely manual labor, even the constant factor – the number of dynamic levels – makes a significant difference). This is one example of why sampling techniques per se arguably do not provide a silver bullet for authentic virtual instruments: although more realistic representations can be achieved by increasing the number of samples, the method can not be made efficient because of the inherent requirements of the sampling process.

Examples

Below are a few sonic examples of a viola virtual instrument utilizing the interval sampling method (the project was conducted in the Sibelius Academy in 2009). First, a comparison between a true recording of an interval, the same interval played with a virtual instrument using ‘conventional’ sampling, and the interval played with a virtual instrument using ‘legato’ sampling.

  • Authentic recording

    An unprocessed recording of an interval

  • Conventional sampling

    The sampling process here is in fact not truly conventional; this example utilizes a primitive legato sample processing technique, where the onset of the second note has been cut

  • Legato sampling

    This example uses the interval legato sampling method described above

In context

These examples demonstrate the legato interval sampled viola together with accompanying instruments.

Illustration