Buchla Music Easel

This legendary and sought-after Buchla synthesizer from the 200 series will be produced again after 40 years. There are some minor changes here and there but in general it´s pretty much the same as the original, a really well-though semi-modular instrument with great sound and lots of possibilities due to well-arranged patch points. The small sequencer and the touch keyboard with integrated arpeggiator invite to play the instrument directly and to interact with it what is great fun and can create interesting polyrhythmic patterns. MIDI functionality is limited to Note On/Off and to synchronisation of the arpeggiator to MIDI Clock. When synched to MIDI the arpeggiator rate control acts as clock dividion control and allows for triplets and ohter divisions.

At the first glance the Easel looks confusing because of the too many switches, faders and many sockests without legending but in the end everything makes sense and it's laid out very logically. The colors of sockets mostly match the function blocks of the Easel (purple = keyboard pressure, yellow = pulser, white = random, orange = envelope, blue = sequencer). The black sockets are CV inputs that are located always left of the according parameter. The sockets at the top of the unit have legending and are self-explaining. The position of most banana sockets below the faders has been chosen for the use of shorting bridges instead of patch cords which enhances clarity of your patch.

The sound generators of the Easel is basesd on a complex main oscillator and a modulation oscillator. The latter is generally used for modulating the main VCO but it can act as a second VCO and it will be routed into the 2nd Lopass Gate, see below.

The main oscillator can be tuned with the frequency fader over 5 octaves and the response to incoming CV can be changed with the +/- polarity switch. The wave form is depending on the sontrols in the timbre section: With timbre fader and timbre potentiometer set to zero we will get a sine wave. Turning up the timbre potentiometer the waveform blends to a sawtooth, a square or a triangle, depending on the switch. The timbre fader modifies this wave form by the use of a wave multipiler for sounds with high harmonic content.

The modulation oscillator has no timbre section, only switchable waveforms (saw, square or triangle). In HI mode it's a VCO, in LOW mode it's a LFO. It's frequency can be modulated also by the keyboard (switchable) or a CV. A switch determines how the modulation oscillator affects the main oscillator, either as a ring modulator, for amplitude modulation or for frequency modulation. The modulation intensity is set with the modulation fader but can be voltage controlled, too.

The oscillator(s) are processed with the Lopass Gates (LPGs). Those are vactrol-based circuits with organic behavoiur and can operate as lowpass filters, as VCAs (gate) or as a combination of both. The audio signal for the 1st LPG is always the main VCO. The second LPG is 180° phase shifted and has a flexible routing: either output of LPG1 (what creates highpass sounds due to the shifted phase), the modulation oscillator or an external audio signal. The outputs of the LPGs are mixed in the output section and their levels can be set separately. Behind the mixer there´s a real spring reverb with dry/wet control providing for more depth in the Easel´s sound when desired.

The Easel can be played with the touch keyboard and/or the sequencer. The keyboard senses the amount of skin touching it, resulting in a pseudo pressure sensitivity. It has a range of 2.5 octaves but you can transpose octaves with the four pads on the top right. While normal playing it senses one finger that determines the pitch, but when using the internal arpeggiator all fingers are analyzed. The arpeggiator has it´s own tempo control and cyn be synched to MIDI.

The Pulser is an impulse generator you can use as a clock source or as a second LFO. It can self-repeat or be triggered by key gate or the sequencer. The envelope is an AD or a ASR type, depending on the setting and can be triggered by the pulser, sequencer or the keyboard gate. The analog sequencer has three, four or five steps and features steps gate switches; it´s gate source can be the pulse or the keyboard gate. Interaction of the switch settings and the simulaneous keyboard play can result in really interesting poly-rhythmical structures.

The four touch pads mentioned above can´t only transpose the octaves; in "preset" setting four pre-set fixed voltages can be played to alter the pitch or other parameters.

Memory is possilbe as well; you need to copy all connections and fader positions by soldering resistors etc. on a PCB memory card. The Easel can either read the values of the memory card, settings of the face plate controls or a combination of BOTH, which gives you three sounds at the same time! A planned interface for iOS devices will simplify memory a lot.