The Web Audio API

MP3 Player with filter and graphics

This will play one of my songs. The upper chart shows the song's frequency domain and the lower chart the song's waveform.
You need to configure the audio before playing the tune, whether you require the filter or not. The filter will default to a zero gain low shelf.
Use the PLAY and PAUSE buttons for finer control over the charting. See Notes below.

The frequency chart appears to span a range from 0 to about 9000Hz.

1. Q controls the width of the affected filter frequency band. The higher Q is the narrower the band. Q is used with all types except lowshelf and highshelf.
2. Gain is only used with lowshelf, highshelf and peaking and can be positive or negative. Be careful with the gain since it quickly leads to distortion.
3. Try setting the filter to lowshelf with a frequency of 1500Hz and a gain of -100. This will wipe out most of the low-frequencies.
4. Try setting the filter to Notch with a frequency of 4000Hz and a Q of 0.7. You should see a "dead" space around the middle of the frequency plot indicating the approximate 4000Hz mark. The lower the value of Q the wider the affected frequency band. If you set Q to zero you will get no plot at all!
5. Try setting the filter to Peaking with a frequency of 4000Hz and a Q of 1 and gain of -60. This will wipe out most of the mid-frequencies.