Legacy mode is turned off by default, because features will become available whenever a compatible music application starts an audio session while Wavelet is running. If no features show up while you're playing music, you can try enabling legacy mode and see if Wavelet will process your music in this mode.
Spotify, YT music, Shuttle, Phonograph and Google Play Music open audio sessions, thus features in Wavelet will show up. Tidal, YouTube, Soundcloud, Qobuz, Neutron, VLC, foobar2000, PowerAmp (with Direct Volume Control disabled) and most music apps that came preinstalled on your phone might work in legacy mode, depending on your device manufacturer's audio framework implementation.
You will have to experiment with legacy mode and see what works best.

By enabling clipping reduction, you allow Wavelet to process audio in a bigger time frame (150 vs 22ms) This reduces clipping at cost of increased latency. Recommended when listening to music but not when watching videos.

The AutoEq feature contains precalculated results from jaakkopasanen's great work. Over 2300 entries are shipped with Wavelet and contain the optimal frequency response compensation for those specific headphone models.

• Headphone model lets you search the database or view your previously selected headphones. Tap the search icon next to the title to add new listings or tap the x icon to remove an item if you selected the wrong one. Make sure to only use the entry that is meant for your headphone model.

The graphic equalizer consists of 9 bands. You can set each slider independently to change the balance in frequency response or to remove obvious imbalance issues. You can also use this feature to compensate the frequency response of your speakers or your headphones if they're are not listed in the AutoEq section, or if you would like to add some coloration to your audio stream.

• Presets contains a few presets for a given set of sound signatures. The first entry will reset all bands to stock.

Bass boost amplifies the lower frequencies.

• Bass boost strength lets you set the strength.

Reverberation adds the effect of a sound bouncing of the wall from a room you would be listening in.

• Preset lets you choose the room size.

Virtualization is the effect of spatializing audio channels. This effect will widen the stereo image (when listening in stereo).

• Strength determines the effect strength.

Bass tuner allows you to set a very precise bass boost or reduction. This can be useful if your speaker system has a resonant peak in the lower frequencies or a point where long soundwaves cancel each other out.

• Cutoff frequency determines until what frequency the sound is processed.

• Post-gain sets the gain to compensate for. This value can either be negative or positive.

The limiter removes volume spikes from your audio streams. Sometimes this is desired in noisy environments where you need to turn up the volume in quiet parts of the music and later turn it down when the music becomes louder.

• Attack time determines after how many milliseconds the effect will kick in. A fast time will help remove unwanted peaks very effectively, but is very noticable. A longer attack time might not be fast enough, but it will sound more natural.

• Release time determines how long the effect will be active. A fast time will give that pumping sound. A long time will sound smoother, but may negate a fast attack time and affect transients in your music.

• Ratio sets the effect strength. If a signal is 1dB over the threshold, it will reduce the output by the ratio level you set.

• Threshold determines above what volume level the limiter should become effective.

• Post-gain allows you to compensate for volume changes caused ratio and threshold.

Channel balance allows you to control the left and right channel output volumes separately. This can come in handy when you can't sit in center of your speaker setup or when your headphones have a difference in impedance between their left and right channels. Some phones have a limiter built in that causes volume ducking when you boost above a certain amount of dB. You can also use this feature to control the overall volume output and to prevent this ducking from happening.

• Channel gain controls the balance between left and right.