Will "Engine" melodies always sound the same?

HouseEngine, TranceEngine, and ChilloutEngine are using a deterministic randomization technique. This means that when you use the same chords and the same scale, you will always receive the same output.

Here's some more background info, as it makes a difference which preset type you work with:

Presets that work directly on the chords (like most basslines or the arpeggios) can sound similar when the chords are similar. This is because they always use the same rhythm/pattern, but apply the playing style to the different chords.

Presets like lead melodies rely on the scale and other factors that are specific to the used chord progression. The different presets also use the same rhythms, but the melodies (pitch curves) are always created from scratch when the input chords and the input scale change.

It's a good idea to differentiate between "bread and butter stuff" and "lead stuff". Offbeat bass, polyrhythmic bass, syncopated chords, etc. are "bread and butter". Millions of songs use the same rhythms for the basslines, and everything is fine. As soon as something is becoming more important for the unique atmosphere of a song, more changes are needed. This is why the lead melodies are using generative melodious shapes. Using the same technique on an arpeggio wouldn't make much sense, as a "random arpeggio" wouldn't be useful for most songs.