Audio characteristics and algorithms

For the display and editing of different types of audio material, Melodyne employs different algorithms. Here, we outline which algorithms are available and for which types of audio material each is used.

The detection process

Melodyne analyzes the audio material to find the notes it contains and offer them to you for editing. We call this process “detection”.

In the course of the detection process, Melodyne itself takes a view as to what kind of material it is confronted with and decides which algorithm to use for the display and playback of the notes. You can tell which algorithm is selected at any given time by the check mark in the Algorithm menu as well as by the blobs in the Note Editor. Please bear in mind, however, that the detection process – in particular in the case of polyphonic audio material – cannot, for reasons that have to do with immutable principles, always deliver perfect results. Since a musically correct analysis of the recorded material is the most important precondition for efficient editing and convincing acoustic results, we recommend you to check the results of the detection systematically and make whatever corrections are necessary.

The Melodic algorithm

Melodic material is monophonic, by which we mean it is such that only one note is ever sounding at any given instant. Please bear in mind, however, that reverberation can cause notes to overlap even in monophonic material, creating, in effect, a kind of polyphony. If melodic material is to be edited in Melodyne, therefore, you should aim for as clean and “dry” (reverberation-free) a recording as possible.

The blobs representing notes in melodic material are displayed at different pitches. Whether the blobs are isolated or joined to other blobs depends on the way they were played or sung: staccato or legato.

The Percussive algorithm

This category includes not only recordings of drums and other percussion instruments but also noise and atmospheric effects as well as other material in which Melodyne cannot detect any clear pitch in the sounds. When the Percussive algorithm is selected, successive drum strokes (for example) are distinguished, but they are all displayed at the same pitch. The blobs can still be raised or lowered in pitch, but the pitch ruler does not display the names of any notes but simply relative values in semitones. The scale functions are deactivated.

The Polyphonic (Sustain/Decay) algorithm

In Melodyne, thanks to DNA Direct Note Access, notes can be detected and edited within recordings even of polyphonic instruments such as the piano or guitar – including the individual notes of which chords are composed. When the Polyphonic algorithm is used, the blobs are displayed in a similar manner to those of monophonic material, with the obvious difference that the blobs are stacked vertically (at their respective pitches) whenever a chord or harmonic interval sounds.

There are two versions of the Polyphonic algorithm:

  • Polyphonic Sustain is the algorithm with which users of earlier versions of Melodyne are already familiar and is suitable for a wide range of polyphonic audio material.
  • Polyphonic Decay is a variation of this algorithm that is particularly suitable for highly percussive signals within which, however, a tonality is discernible.

Please note that DNA is designed for tracks containing a single polyphonic instrument (a guitar, a piano, ...) and that it divides the material up according to pitch – not instrument. If two instruments play the same note at the same time, what is available for editing is a single note comprising the combined sound of both instruments.

NB: There is some audio material that cannot be detected using the polyphonic algorithms because it contains too few tonal components. If in the case of such material you have chosen one of the polyphonic algorithms as the default (see below), the polyphonic detection process will be interrupted and a fresh detection of the material using the Percussive Algorithm, which is better suited to it, will commence. If you wish in such cases, when this detection is complete, you can still switch to Universal or Melodic.

The Universal algorithm

The Universal algorithm is particularly suitable for complex signals containing both percussive and tonal elements. If, for example, you wish to alter the pitch, timing or tempo of an entire piece of music, this algorithm will deliver the best sound quality.

The Universal algorithm, like the Percussive one, displays all the detected notes at the same pitch. The Pitch Ruler displays no note names, merely relative values for the semitones, and the scale functions are deactivated. The Universal algorithm completes the detection process very quickly and also consumes far fewer resources than the Polyphonic algorithm. It represents a good choice, therefore for recordings of individual instruments of all kinds that you intend simply to speed up, slow down or transpose. Tracks, in other words, for which you do not need bells and whistles such as DNA or Melodyne’s scale functions. Please note that with files that have been detected using the Universal Algorithm, the Attack Speed Tool cannot be used. Attack speed handles will therefore not be displayed for the corresponding blobs and the Attack Speed field in the Note Inspector will be grayed out.

Switching algorithms

You can at any time select a different algorithm to that chosen automatically for you by Melodyne. You might want to do this, for example, if you find that the material has not been interpreted in a way that suits your editing needs. To do this, while playback is halted, select the algorithm you prefer from the Algorithm menu. Melodyne will reinterpret the material in the light of your choice and adjust the display accordingly.

Note: when you do this, any editing of the same track performed prior to switching algorithms, including any copying of notes, will be lost (copied notes on other tracks are retained) . The right time to decide which algorithm you wish to use, therefore, is before you begin editing.

In the plug-in implementation of Melodyne, the choice of algorithm applies to an entire transfer, in the stand-alone implementation, to an entire audio file in the document being edited – collectively, we describe all such material as ‘audio sources’. Before you can change the algorithm applied to a particular audio source, you must first select one or more notes belonging exclusively to it. If you have selected no notes, or notes from two different audio sources, the Algorithm menu will be grayed out. In such cases, reduce your selection to notes belonging to one audio source only and it will be possible to switch algorithms.

When you switch algorithms, triggering a fresh detection, Melodyne looks at the status of the Auto Stretch switch: if the Auto Stretch function is activated, once the new detection is complete, the tempo of the file will also be adjusted: if Auto Stretch is not selected, the original tempo of the file will be retained.

Automatic or manual algorithm selection

Melodyne by default selects the most suitable algorithm automatically, basing its choice on the characteristics of the audio material. If, however, in an instance of the plug-in implementation of Melodyne or on a track of the stand-alone implementation material has already been detected, when new material is transferred to that instance or a new file dragged into the track of the stand-alone implementation, Melodyne will use the same algorithm for the new material as it used for the old – even if Automatic is selected.

Overruling the Automatic setting in this way is designed to ensure maximum consistency in the detection and avoid all risk of one of the transfers from a vocal track suddenly being interpreted as percussive. If, however, you have altered the algorithm of a transfer or file manually, the automation kicks in again afterwards, and no further attention is paid in the case of further transfers or files to already detected material.

This rule only applies when Automatic is selected as the algorithm. It does not apply, however, when you are using Melodyne with ARA; nor when, in the stand-alone implementation of Melodyne, a new file for which an MDD file already exists, containing the editing applied to its detection, is dragged into a document

By setting a different default via the Algorithm menu, you can prevent Melodyne selecting an algorithm automatically for the detection. This can be useful if, for example, you regularly want to edit particular files using the Percussive algorithm but Melodyne, each time they are opened, is interpreting the material as polyphonic. By preselecting the Percussive algorithm in such cases you can save time, as you will no longer have to wait needlessly as Melodyne performs its polyphonic analysis, only to discard the results moments later when you manually select the Percussive algorithm.

Do not forget, however, when you no longer need to impose your choice of algorithm on Melodyne, to restore Automatic as the default setting. Otherwise, since Melodyne remembers your default selection even after you have quit the program, you might be surprised to discover when the program is next launched that your vocals have been interpreted as percussive.