KeyboardAudioVisualizer/KeyboardAudioVisualizer/AudioProcessing/Spectrum/ISpectrum.cs

using System.Collections.Generic;

namespace KeyboardAudioVisualizer.AudioProcessing.Spectrum
{
    public interface ISpectrum : IEnumerable<Band>
    {
        int BandCount { get; }

        Band this[int index] { get; }
        Band this[float frequency] { get; }
        Band[] this[float minFrequency, float maxFrequency] { get; }
    }
}