# Psychoacoustic Approaches for Harmonic Music Mixing +
## 4 Evaluation
### Listening Test  
To evaluate the ability of our model to provide consonant mixes between different pieces of music, we conducted a listening test using excerpts from our dataset of 30 short musical excerpts of recent house music (each 8 s in duration and lasting exactly 16 beats). While our main concern is in evaluating the properties of the roughness curve, we also included a comparison against a key-based matching method using the key estimation from the well-known DJ software Traktor 2 (version 6.1) from Native Instruments [28]. In total, we created five conditions for the mix of two individual excerpts, which are summarized as follows:  
* **A** No shift: no attempt to harmonically align the excerpts; instead, the excerpts were only aligned in time by beat-matching. * **B** Key match (Traktor): each excerpt was analyzed by Traktor 2 and the automatically-detected key recorded. The key-based mix was created by finding the smallest pitch shift necessary to create a harmonically-compatible mix according to the circle of fifths, as per the description in the Introduction. * **C** Max roughness: the roughness curve was analyzed for local maxima, and the pitch shift with the highest roughness (_i.e._, most dissonant) was chosen to mix the excerpts. * **D** Min roughness: the roughness curve was analyzed for local minima, and the pitch shift with the lowest roughness (_i.e._, most consonant) was chosen to mix the excerpts. * **E** Min roughness and harmony: from the set of extracted minima in Condition **D**, the combined harmonic consonance and roughness was calculated, and the pitch shift yielding the maximum overall consonance \(\rho|s^{*}|\) was selected to mix the excerpts. We selected the set of stimuli for use in the listening experiment according to two conditions. First and foremost, we required a set of unique pitch shifts across the five conditions per mix, and second, we chose not to have any repeated excerpts either as input nor the track to be pitch-shifted. To this end, we calculated the pitch shifts for each of the five conditions for all possible combinations of the 30 excerpts in the dataset (introduced in Section 3.1) compared to one other. In total, this provided 900 possible combinations of tracks (including the trivial comparison of each excerpt with itself). A breakdown of the number of matching shifts among the conditions is shown in Table 1. Bydefinition, there were no matching pitch shifts between Conditions **C** (max roughness) and **D** (min roughness) or **E** (min roughness and harmony). By contrast, Conditions **D** and **E** matched 385 times. Out of 900, a total of 409 combinations gave unique pitch shifts across all five conditions. From this subset of 409, we discarded all cases where the smallest pitch shift between any pair of combinations was lower than 0.25 semitones. Next, we removed all mixes containing duplicate excerpts to avoid single tracks in more than one mix. From this final subset, we kept the 10 mixes (listed in Table 2) with the lowest maximum pitch shift across the conditions. In total, this provided 50 stimuli (10 mixes \(\times\) 5 conditions) to be rated. A graphical overview of the pitch shifts per condition is shown in Figure 10, for which sound examples are available in the Supplementary Material. All of the stimuli were rendered as mono.wav files at a sampling rate of 44.1 kHz and with 16-bit resolution. In total, 34 normal hearing listeners (according to a self-report) participated in the experiments. Their musical training was self-rated as being either: music students, practicing musicians or active in DJing. Eleven of the participants were female, and 23 were male; their ages ranged between 23 and 57. When listening to each mix, the participants were asked to rate two properties: first, how consonant and, second, how pleasant the mixes sounded to them.