via
this auction
"974-75 ARP EXPLORER I, model#2900, first version/mark 1... I got most of my information from www.vintagesynthexplorer.com so please visit that site, however it's a rarer ARP synth, my version is earlier than the unit pictured on that great site, the info is limited so here are a few more specifics:
The ARP Explorer model 2900 has only one oscillator but same design as used in the production of the larger model 2600. The ARP Explorer has the same oscillator and controls(plus noise waveform) and effects section(plus portamento and auto-bend) used on the popular ARP LITTLE BROTHER. Unfortunately only one each 1/4 and RCA mono outputs.
The Explorer I uses the same chassis and endcaps as the PRO-SOLOIST, same 37 key keybed, Explorer has no aftertouch.
This Explorer I 2900 first version has the same panel cosmetics (gold lettering on black) and slider tip color scheme of the 1974-76 Odyssey Mk II
Combination of subtractive and semi-additive (one oscillator) synthesis with 4 pitch ranges , select one, all, or any combination. Five waveforms, select one, all, or any combination.
Pitch bend knob with 1 octave up or down keyboard range just like Mk 1&2 Odyssey.
Switchable between preset and manual mode for both ADSR section and filter section- a standard gate is the ADSR "preset", the filter is a 4-pole lowpass filter with cutoff and res.
LFO has separate level control in the upper section, and in the lower effects section, speed and vibrato depth, with vibrato delay on/off, or a single-note sample-and hold or perpetual "repeat" with "auto" or "KYBRD" modes also using the LFO speed as repeat rate.
Nice and dark sounding, warmth, and obviously a very 1970s sound."
Goldbaby just released Tape Drum Machines Vol. 3. You'll find samples on site. Be sure to check out their other samples sets as well. Each one has a pdf link with tons of shots and info on what went into them, in a very cool, comic book, format. Below are captures of Vol. 3. "Vol 3 contains: 12 Drum Machines and 3 Tape Machines. 3498 x 24 Bit drum samples Drum Machines used: RZ-1, TR-55, XD-5, MFB-522, DDM-110, DDM-220, DPM-48, RX-21L, R-100, ED-10, PB-300 and the DSM-1. The Tape machines used: Otari MX5050 1/4", Rolla 77 valve mono 1/4 inch, and the Hitachi Cassette deck. Plus the UBK Fatso was also used! Formats: Battery 3, Guru and Wav Pack" 
The list: MPC Electronics DSM-1 KORG Super Drums DDM-110 KORG Percussion DDM-220 Yamaha ED-10 MFB 522 Roland TR-55 Roland PB-300 Casio RZ-1 Sakata DPM-48 Yamaha RX-21L Kawai XD-5 Kawai R-100 Rolla 77 MK3 / MKIII Kush UBK-Fatso Otari MX5050 1/4 inch Hitachi Cassette Desk Update: video added below. 
