Roland TR-505

The Roland TR-505 rhythm composer is a drum machine and MIDI sequencer released by Roland Corporation in 1986.^[1][2] It hails from the same family of drum machines as the Roland TR-909, TR-808, TR-707, TR-626 and TR-606. The drum kit includes basic rock drum sounds similar to those of the TR-707, plus a complement of Latin-style drum sounds similar to the TR-727.^[3][4]

TR-505
The Roland TR-505
Manufacturer	Roland Corporation
Dates	1986–1991
Price	$318 US (1986)
Technical specifications
Polyphony	8 voices
Oscillator	N/A
Synthesis type	Digital sample-based
Velocity expression	No
Storage memory	Patterns: 48 user, 48 preset. 6 Songs.
Effects	No
Hardware	Main panel features a simple LCD display, 15 buttons, 2 knobs, 16 trigger pads, 2 outputs for left and right/mono, headphone jack, and tape input/output.
Input/output
Keyboard	16 pattern keys
External control	MIDI in/out, start/stop foot pedal jack.
Audio sample	8-bit unsigned PCM data, with a 25.00 kHz sampling rate

Voice synthesis

Samples in the TR-505 are stored as 8-bit unsigned PCM waveforms at a sample rate of 25 kHz. The TR-505 offers some major improvements over the TR-707, including 16 digitally recorded PCM drum sounds (four more than the TR-707) and five Latin percussion voices from the TR-727, reducing the need to buy a separate unit or PCM card.^[5][3]

Summary of drum voices:^[6]: 9

Low conga	Hi conga	Timbale	Low cowbell	Hi cowbell	Clap	Crash	Ride
Kick	Snare	Low tom	Mid tom	Hi tom	Rimshot / sidestick	Closed hi-hat	Open hi-hat

Although there are 16 drum samples, the TR-505 only has an 8-voice polyphony, restricting some sounds from playing simultaneously: low conga or hi conga; timbale, low tom, mid tom, or hi tom; low cowbell or hi cowbell; hand clap or rim shot; crash cymbal or ride cymbal; closed hi-hat or open hi-hat.^[6]: 9

The TR-505 offers very limited voice editing in the form of volume, velocity, MIDI channel, and MIDI note of each voice as a global parameter.^{[6]: 14,40,42}

Sequencer

The TR-505 contains 48 factory sequencer patterns, organized into 3 pattern groups (A, B, and C). The drum machine can also store 48 user created sequencer patterns, organized into 3 pattern groups (D, E, and F).^[3]

The TR-505 features five basic modes, including the following:^[6]: 8

• Track play - plays whole tracks (arrangements of patterns to form songs).
• Track write - sequence patterns into tracks.
• Step write - sequence patterns by stepping through each position in the pattern.
• Tap write - sequence patterns by tapping drums sounds in real time.
• Real time - play patterns in real time by tapping the pads.

An accent can be applied to any position in a pattern and will affect all instruments triggered at that position by increasing output volume.^[6]: 15

Users can copy, insert, or delete one or more steps in any given pattern, and copy, insert, or delete patterns anywhere in a track (song).^[1]

Each individual pattern is a single measure long, The default time signature is 4/4 consisting of 16 steps and quarter note scale, resulting in each step representing a sixteenth note. Other time signatures can be programmed by changing the Last Step (length of patterns) and the scale, allowing for shuffle and swing rhythms.^[6]: 24

Two or more patterns can be combined, using pattern chaining, to play as a single pattern. Each pattern in the chain occupies a pad, but it will only trigger the chain as a whole, not the individual pattern.^[6]: 27

Up to six tracks (songs) can be programmed using combinations of patterns.^[6]: 16 Each song can consist of up to 423 bars (patterns).^[7][6]: 18

Keyboard and external control

The TR-505 consists of 16 individual instrument/ pattern pads.^[7] The pads are not velocity sensitive, but can be modified by the accent parameter.^[6]: 51

The TR-505 can transmit and receive on MIDI channels 1 through 16 and Notes numbers 25 to 99. It also contains a MIDI Omni mode allowing it to receive all MIDI data. The TR-505 responds to the following MIDI messages:^[3]

• Key message - trigger signal for the individual voice.
• Velocity message - Note-on velocity is both transmitted and received allowing more expressive.^[6]: 51
• Track number message - track/song select
• Bar Number message - Song position
• Clock message - tempo synchronization, start, stop, etc..

Storage

The TR-505 can store 48 ROM patterns, 48 RAM patterns, 6 tracks, and a maximum of 423 measures.^[8]: 1

The Tape interface (in/out) allow the Tracks and Patterns in internal memory to be stored on external tape.^[5] Data can be Saved, Verified, and Loaded from the tape.^{[6]: 35,36,37}

Modifications

There are companies, websites, and magazine articles documenting a DIY process for circuit bending and modifying the factory setting of the Roland TR-505. An example of a few modifications include changing audio samples,^[9] voice circuit bending,^[10] adding individual audio outputs,^[11] adding CV outputs,^[12] adding pitch change to each voice,^[10] and adding circuits to randomize sequences.^[10]