A generation of musicians have now begun their programming careers with a little help from the Doctor... Now he's back with two new drum machines which continue the tradition of affordable technology designed on a human scale.

For a company who have traditionally enjoyed a commanding presence in the drum machine market, Roland have not had the best of times in the past year or so. While the 'middleground' of the market has been dominated by Alesis' SR16 beatbox, Yamaha have seized the initiative from Roland at the high end with the RY30. Roland's chief success has been with their Boss division's budget DR550 drum machine (reviewed MT May '90), which at £199 has single-handedly defined the low end of the market since its release in 1990.

However, 1992 is turning out to be biteback time for Roland. With the recently-launched R70 (reviewed MT July '92), the company are attempting to regain the prestigious high-ground initiative by offering a leading-edge machine packed with all the proverbial bells and whistles. Meanwhile, more modest in both design and intention, the new DR550 MkII sees the company updating the original 550's spec in an attempt to hold on to the budget market - but charging £26 more for the new machine in the process. In fact, Roland are still producing the original 550, so budget-minded buyers can choose between the two machines.

Rounding out the new line-up, the 550 MkII is complemented by a second addition to the Dr Rhythm range, the DR660. Designed to compete head-on with the SR16 (reviewed MT February '91), the 660 is the most sophisticated DR beatbox to date - with a price tag to match. Unfortunately for Roland, Alesis have responded by slashing the price of the SR16 from £349 to £259. So has the DR660 been left high and dry? And will the DR550 MkII, priced less competitively than the original 550, be able to weather the storm of tough competition from Yamaha's new RY10 budget beatbox (£249) and the born-again SR16?

With the emphasis, these days, on providing plenty of kicks and snares on drum machines, the 550 MkII's complement of 11 kicks and 18 snares seems small when compared to other machines currently on the market. In fact, the 550 MkII's total of 91 onboard sounds (which only three years ago would have been considered impressive on a machine costing twice as much), is rather limited when set against the RY10's 211 sounds or the SR16's 233. Its nearest competitor, the RY10, provides a more diverse collection of sounds, including off-the-wall sound effects and a variety of bass sounds, and offers a lot more kicks and snares. The two machines also differ in sonic character - the DR550 MkII has that familiar crisp, clear, punchy Roland sound, while the RY10's is grittier and somehow more 'colourful'.

Unlike the DR550 MkII, the RY10 allows its sounds to be tuned, albeit over a limited range; however, by way of compensation, the 550 MkII does boast a tone colour parameter as a means of altering its sounds. Continuing with the comparisons, the RY10 offers 28-voice polyphony against the 550 MkII's 12 voices and provides 50 preset and 50 programmable patterns (each with an associated fill pattern), while the MkII has 64 of each type (with no fill patterns). And, while the MkII has four pad banks which are common to all its patterns, the RY10 has 32 pad banks which are assigned singly to individual patterns.

Unlike the RY10, the 550 MkII doesn't implement realtime song recording, nor does it have a guitar tuner function, or an audio input allowing an external signal to be routed to the tuner or merged with the drum machine's own signal. It's also worth noting that the RY10's headphone output is louder and punchier than that of the 550 MkII - an important consideration for portable use - though I found that I was able to hear the MkII's output without difficulty while programming the drum machine during an averagely noisy train journey.

Mention of portable use brings us to the similarities between the two machines, perhaps the most notable being their ability to run off six AA-type batteries. The DR550 MkII is the smaller and lighter of the two machines, and can run for longer - approximately 23 hours compared to approximately 14 for the RY10.

While this shared ability brings freedom, other similarities between the DR550 MkII and the RY10 impose limitations. Both beatboxes have non-backlit LCDs and non-dynamic playing pads, limit their pattern lengths to a maximum of 16 steps, have a maximum record resolution of a 1/32nd note, allow their sounds to respond to velocity via MIDI but won't record incoming velocity data, and provide a MIDI In socket but no MIDI Out. The absence of a MIDI Out socket means SysEx data dumps of pattern and song data aren't possible, so both machines provide a tape save/load option instead.

The other new Dr Rhythm, the DR660, provides more sounds than either the SR16 or the more expensive R70 - 254 compared to 233 on the SR16 and 210 on the R70. In fact, what you're getting is most of the R70's sounds with new sounds added. These 254 sounds break down into 50 kicks, 72 snares, five side sticks, 39 toms, 11 hi-hats, seven cymbals, 36 percussion instruments, 16 effects, 11 reversed versions of selected sounds, five ambience samples and two basses (slap and synth).

As with the overall number of sounds, the number of kicks and snares on the 660 surpasses both the SR16 (49 and 59 respectively) and the R70 (just 28 and 45 respectively). The resulting sonic variety is impressive indeed. The quality is, of course, all that we've come to expect from Roland - the company don't compromise as the machines get cheaper.

The DR660 has 100 preset and 150 programmable patterns. Pattern length can be up to 80 beats (enough for 20 4/4 bars), while maximum record resolution is 96ppqn. Quantisation on the 660 is record only. The 660's 16 playing pads provide both velocity and aftertouch responsiveness, and performance dynamics can be recorded into a pattern. Once a pattern is looping in real-time record mode, you can drop in and out of record at any time by pressing the Record button; this lets you locate a sound or try out a new part without having to stop the drum machine playing.

Individual recorded parts can be deleted in real-time by holding down the Delete button and pressing the relevant pad(s). You can also delete whole patterns, and copy a recorded pattern from one memory to another. Flams and rolls can be recorded for any part by holding down the dedicated Flam and Roll buttons while playing the relevant pad. Roll interval and flam interval and ratio can be programmed, and the aftertouch sensitivity of the pads can be used to dynamically alter the level of the roll.

'Macro' pattern editing functions are limited to swing (programmable on quarter, 8th, 16th or 32nd notes for a whole pattern, with swing amount ranging from 50-80) and timing shift (pad-specific, ±96 clocks in single-clock steps). Patterns can also be recorded and edited in step time. Like everything else about the DR660, step-time input is straightforward in implementation and easy to use, yet also flexible in application.

The DR660 picks up on the SR16's concept of having programmable variation and fill-in patterns for each main pattern, but implements it a little differently. Whereas on the SR16 you program A, B, Fill A and Fill B patterns for each pattern number, on the DR660 you select other pattern numbers for your Variation, Fill-to-Original and Fill-to Variation patterns. The 660's approach allows you to try out different groupings of patterns very quickly, so that, for instance, you could try out a pattern with a variety of fills.

"The DR550 MkII provides almost double the number of sounds on the original machine - adding 43 to the 48 on the original"

Once they're assigned to a pattern, the variation and fill patterns can be selected in real time using the Start, Forward and Backward buttons while the machine is running. Fill patterns, of course, drop in immediately when selected; you can drop in a fill on the first beat of an original or variation pattern, but a fill pattern can't repeat.

Like both the SR16 and the RY10, the DR660 opts for pattern-specific Drum Kit assignments, rather than the R70 approach of allowing any sound from any of its pad banks to be used within each pattern. The 660 has seven preset and 32 programmable Drum Kits, any one of which can be assigned to any pattern. Kits provided include Power, Electro, TR808, TR909, Jazz, Brush, Ambient, Pop, Dance, Percussion, Reggae and FX. You can select a different Drum Kit for a pattern at any time - even while recording or playing back the pattern - so experimenting with different combinations of rhythm and sound is easy.

Working like this can lead to some inspired results which you probably wouldn't come across otherwise. Other 'chance' possibilities are available by switching between independent and layered pad bank modes. Each Drum Kit consists of two pad banks, A & B, which can be used to provide 32 single sounds (ie, 2 x 16 pads) or 16 layered sounds per pattern. In practice, limits are placed on the density of patterns by the DR660's 12-voice polyphony and the fact that a maximum of nine sounds can be entered for each pattern step.

Each pad within each pad bank can be assigned a sound together with settings for level, pitch ± octaves in ten-cent steps), decay, nuance, pan, assign type (mono/mono exclusive 1-7/poly/poly exclusive 1-7), and velocity response curve. With this last parameter you can not only tailor the velocity response of individual sounds, but, by assigning positive and negative curves to layered sounds, also create velocity crossfades.

Along with these parameters, you can assign each pad its own MIDI transmit/receive note number, allowing MIDI'd sounds to be triggered as part of a DR660 pattern. In practice, though, you're limited in the sort of instrumental parts you can play in this manner as the drum machine transmits all MIDI notes with the same, short duration.

In addition to its pad-playable sounds, each Drum Kit has a further 23 sounds which are accessible only via the 660's MIDI In socket. You can't record parts for these extra sounds into a DR660 pattern, but obviously you can trigger the sounds from a MIDI sequencer - or just use them for live playing.

Drum Kits can be called up remotely via MIDI using patch change commands, an essential feature if you're using the 660 purely as a MIDI sound source. What you can't do is call up DR660 patterns remotely as part of an external sequence, so all pattern changes have to be recorded on the drum machine itself as a song. The 660 allows you to create up to 100 onboard songs. An individual song can have up to 250 parts (single-pattern steps) - drawn from an overall capacity of 1000. A song-chain function allows you to treat individual songs as song sections; as each song can be given its own initial tempo, working this way allows you to have tempo changes within your overall song.

"The DR660 is a well-conceived drum machine which sits very comfortably at the middle level of sophistication"

Like the SR16, the 660 provides real-time song recording in addition to the more familiar step time. This means you can put your songs together by making pattern selections as the patterns play in Song Record mode; you can also switch between Original and Variation patterns and drop in Fills in real time as part of your song. One SR16 feature which the DR660 omits is a footswitch input, so you can't drop in Fills or switch between original and variation patterns with a tap of the foot, nor can you spontaneously 'stretch out' a song on playback by getting a song step to repeat while the footpedal is held down - all useful features of the SR16.

The DR660 scores over Alesis' drum machine with its inclusion of onboard effects processing, which has clearly been adopted from the R70. There are two effects processors, one providing a choice of hall, room, plate, delay and pan delay effects, the other a choice of chorus or flanger. Effect parameters provided (programmable per Drum Kit) are reverb time, reverb LPF, delay feedback, chorus depth and chorus rate. In addition, each pad within a Kit can be given its own reverb and chorus amounts. You can also make live changes to the overall reverb and chorus effect levels while a pattern is playing - you just press the Reverb or Chorus button and turn the data dial.

For separate routing of selected sounds, two individual outs are available in addition to the stereo pair. However, as on the R70, you can't use the reverb processor and Out 1 at the same time, or the chorus processor and Out 2 at the same time - separate routing on the DR660 means using external processing on all outputs.

The DR550 MkII is an ideal drum machine for anyone who wants their technology to be as friendly and inexpensive as possible and isn't bothered about limitations like a 16-step maximum pattern length, a modest recording resolution and an inability to record dynamics. At the same time, the MKII's compact dimensions, light weight and optional battery powering make it worth considering as a portable 'rhythm notepad' by anyone who wants to program on the move. It's worth bearing in mind that, having 'sketched out' some rhythms on the 550 while away from the studio, you can later sidestep all its programming limitations by recreating those rhythms on a sequencer and triggering the drum machine's sounds via MIDI.

But the DR550 MkII doesn't have the budget market all to itself. Yamaha's RY10 (reviewed MT August'92) will also give you battery-powered portability, and it has much the same set of advantages and disadvantages as the MkII but is in some ways a better-specified machine (more sounds, for instance). A little extra money will take you up to another level of sophistication and versatility with Alesis' SR16, which is still easy to use but doesn't give you a battery option. When making your pricing calculations, bear in mind that the SR16 comes with an AC adaptor as standard, whereas it's an extra with the DR550 MkII and the RY10 (£15 extra in the case of the 550's Boss PSA adaptor).

The other new Dr Rhythm, the DR660, is an extremely well-conceived drum machine which sits very comfortably at the 'middle level' of sophistication yet provides the ease of use associated with simpler low-end machines together with a collection of sounds which is definitely the stuff of high-end machines. If you like the idea of having the R70's sounds in a less expensive and more straightforward, approachable machine, look no further.

But is the DR660 effective competition for the SR16? After all, taking into account the additional cost of a BRA power adaptor for the 660, the two machines are a not inconsiderable £100 apart in price. For some people, price alone will be the clincher, especially in the current economic climate, but if your budget will allow for the extra cost, I think you'd have to opt for the 660.