• The Bullfrog is a classical subtractive synthesizer—It consists of several modules for sound generation—VCO, noise generator–and treatment—VCF, VCA/delay, as well as modules that generate control and modulation signals to control them—envelope generators and sample and hold.
• The Bullfrog will not make sound on its own unless you make patches—use patch cables to interconnect the modules, or insert voice cards that create internal connections between the modules in a specific way. This approach better helps to understand functionality of a subtractive synthesizer and the principles of sound design with instruments like these.

• Noise Generator: Generates white noise, a sound that contains all audio frequencies at equal amplitudes mixed together
• Mixer: Individual waveforms with adjustable amplitude are available, as well as a mixed signal where you can define how much of each waveform is sent to the Mix Out. Add external sounds to the three inputs (In 1, In 2, In 3). Inserting a cable into the input will remove the normaled connection.

• VCA: The Voltage Controlled Amplifier (VCA) is the most straightforward module in the synthesizer. Its sole purpose is to alter the amplitude of the signal that leads to changes in volume.
• Delay: The delay circuit takes its signal post VCA and includes a dry/wet knob for controlling how much of the delay signal is mixed with the dry signal. Delay Time controls the length of the delay (30 to 340 ms), while the feedback controls the number of decaying repeats.

• The Divider is a utility module that divides a frequency of the incoming signal by 2, 4, 8 and 16. Normally, such dividers work with pulse-wave signals and have various applications, including computers. But on the Bullfrog, the incoming signal can be any signal, and the divider will advance to the next step as soon as the incoming signal is higher than +3V.
• In music technology, dividers can be used as frequency dividers (remember, a frequency divided by 2 gives you a pitch that is exactly one octave down), to control sequencers, to create drum patterns and for many other applications.

The Bullfrog XL comes with 6 voice cards:

• ACID BASSLINE: Instantly provides you with all necessary connections to produce a punchy bassline.
• SAMPLER-LOOPER: Emulates the functionality of a tape recorder, recording up to 10" of audio from the built-in microphone or from the Bullfrog itself, and then feeds it back into the audio path of the Bullfrog for processing via the VCF, VCA, and Delay.
• HIGHPASS VCF: Expands the sound treatment capabilities of the Bullfrog by exploring high-pass and band-pass filtering.
• ELECTRIC ORGAN: Emulates a pipe organ when several notes are played together. It also illustrates the principles of additive synthesis, where several simpler waveforms are mixed together to generate more complex sounds.
• ANALOG SEQUENCER: compact CV/GATE five-step sequencer that generates up to five steps of discrete control voltages that control a pitch of the VCO and gates that trigger the envelope generators. Audio and CV connections are the same as on the Acid Bassline voicecard.
• LFO VOICE CARD
• BLANK DIY VOICECARDS (x3): Allows you to create custom connections of the Bullfrog modules. The voice card mimics the connection points of the Bullfrog. In order to make connections, you need a wire and a soldering iron (and a bit of soldering skills). Use pieces of a wire to connect the points on the voice card and solder the wire. We recommend first to make connections with patch cables directly on the Bullfrog, and if you like a specific patch, you can make a DIY voice card for it.

Additional Voicecards are available separately for purchase:

• GROOVEBOX: Adds electronic drum sounds to a main synth voice and features two semi-random pattern sequencers—a trigger sequencer for drum sounds and a CV/gate sequencer for a bass line. Essentially, it turns the Bullfrog into a fully functional groovebox.
• WIND AND STARS: Automatically emulates randomly evolving wind sounds and blinking stars are controlled by the divider. (Toddlers fall asleep better when they hear sounds like these.)