Waveguide physical model of a slap bass
This is a physical model of a slap bass, containing a pair of waveguide strings which can hit a fret and buzz when struck hard enough.
The snapshots included in this instrument have been tuned for use with 44.1 kHz sample rate. Other sample rates may require retuning using the controls available on the “String” page.
The graphic control elements were created by Vera Kinter, URL http://www.artvera-music.com.
Some of the controls are self-explanatory, such as Tune, Transpose, Pitch Wheel Depth, and Output level.
“Number of Strings” can be set to either 1 or 2. When set to 1, legato playing can create clicks, and can also build up significant energy in the string, making it more likely to hit the fret. While this may be undesirable when playing a straightforward bass, it can add some nice body to the sound when playing a snapshot that whacks the fret heavily.
There are seven parameter pages: Thumb, String, Slap Fret, Pickups, 10-band EQ, Compressor, and Modulations:
This is the initial excitation of the string, and consists of a short burst of filtered noise. An attack/decay envelope generator controls the excitation’s shape, and a 1- or 2-pole lowpass filter controls the brightness. The Strength control determines how much energy is applied to the string. The pluck point can be moved along the string, or can be turned off. If turned off, the model resembles a Karplus-Strong string.
The string is a standard waveguide model. The decay time and high-frequency loss are controlled by the Sustain and Tone controls. The Release control determines how long the string rings when a note is released. The sustain, tone, and pitch can be adjusted at every fourth semitone (C, E, and G#). These adjustments are useful when programming sounds that remain musical over a wide range of notes. They can also compensate for the tendency of waveguide models to go flat on high notes. Please note that changing the Tone control may make the string go flat or sharp, and require re-tuning.
This is a fret, which when hit by the string, causes the string’s energy to reflect back in the direction it came from. Parameters include the fret’s position on the fret board, the fret’s distance from the string, and the reflection’s gain. The distance between the fret and the string determines how easily the fret will be hit. A lamp indicates when the string and fret are in contact. A switch can disable the slap fret. To make an expressive slap bass, route key velocity to Thumb Strength, and adjust the distance between the fret and the string.
This is the output of the model. Three outputs are provided: an acoustic pickup at the bridge, a movable electric pickup, and the initial thumb excitation impulse.
The 10-band equalizer is the standard Reaktor equalizer, stripped to a single mono channel. There are also two additional filters. The first is called Big Bottom, which tracks and emphasizes the note’s fundamental frequency. The second is called an Acoustic Filter, and is an array of bandpass filters that mimics the resonances in a string bass.
The compressor is the standard Reaktor compressor, stripped to a single mono channel.
MIDI modulations are programmed here. Six busses are provided. Each bus has a source, destination, curvature, modulation amount (both positive and negative) and on/off switch. Sources are various MIDI inputs (mod wheel, velocity, etc.). Destinations are various parameters of the model (attack time, thumb strength, fret position, etc.).