Computes the chroma CQT of the given audio time series using librosa.
The chroma CQT is a representation of the audio signal in terms of its
chromatic content, which is useful for music analysis.
The chroma CQT is computed using the following parameters:
- path_audio_time_series_y: The path to the audio time series (CSV file).
    It's sometimes better to take harmonics only
- hop_length: The number of samples between frames.
- fmin: The minimum frequency of the chroma feature.
- n_chroma: The number of chroma bins (default is 12).
- n_octaves: The number of octaves to include in the chroma feature.
The chroma CQT is saved to a CSV file with the following columns:
- note: The note name (C, C#, D, etc.).
- time: The time position of the note in seconds.
- amplitude: The amplitude of the note at that time.
The path to the CSV file is returned.

Computes the MFCC of the given audio time series using librosa.
The MFCC is a representation of the audio signal in terms of its
spectral content, which is useful for music analysis.
The MFCC is computed using the following parameters:
- path_audio_time_series_y: The path to the audio time series (CSV file).
    It's sometimes better to take harmonics only

Computes the beat track of the given audio time series using librosa.
The beat track is a representation of the audio signal in terms of its
rhythmic content, which is useful for music analysis.
The beat track is computed using the following parameters:
- hop_length: The number of samples between frames.
- start_bpm: The initial estimate of the tempo (in BPM).
- tightness: The tightness of the beat tracking (default is 100).
- units: The units of the beat track (default is "frames"). It can be frames, samples, time.