Using ALSAaudio in Reaper stops all other audio playback?

When I record an instrument through a Focusrite Solo into Reaper (letting Reaper use ALSA), I could play other audio sources at the same time with no problems until recently.

Now whenever I try to play a Youtube video or play a local audio file, neither will give audio but the instrument in Reaper is still audible. Youtube videos will even immediately start buffering indefinitely until Reaper is closed.
It’s like ALSA went back to the old “exclusive” behaviour which it hadn’t been doing for a long time now.

Also worth noting is that this issue doesn’t occur when using JACK in Reaper, but the audio playback within Reaper is a lot more quiet than it is with ALSA, even when playing back the very same audio files.

If I set ALSA to use “default” input and output devices, the volume will become just as quiet as when using JACK and all playback from multiple sources will work fine, but if I use the standard “hw:usb ; USB-Audio - Focusrite Solo USB” as input and output devices, that’s when the playback problems start again, until Reaper is closed or the Focusrite is unplugged (forcing Endeavour to change to a different audio device).

I think regarding both the playback issue and the seperate volume issue, that JACK through Reaper isn’t directly using the Focusrite Solo like ALSA tries to do.

can you report

inxi -Fza
pacman -Qs alsa
pacman -Qs pulse
pacman -Qs pipewire

inxi -Fza

System:
  Kernel: 6.14.4-arch1-2 arch: x86_64 bits: 64 compiler: gcc v: 15.1.1
    clocksource: tsc avail: acpi_pm
    parameters: initrd=\e0ee2436671f43cfaf66ec7f267f5f52\6.14.4-arch1-2\initrd
    nvme_load=YES nowatchdog rw
    root=UUID=e247b1ec-f3ab-4f33-867b-509ad9bcecee
    resume=UUID=38fe6b39-ecdd-43be-b202-63a081f1287b rw
    root=UUID=e247b1ec-f3ab-4f33-867b-509ad9bcecee
    resume=UUID=38fe6b39-ecdd-43be-b202-63a081f1287b
    systemd.machine_id=e0ee2436671f43cfaf66ec7f267f5f52
  Desktop: KDE Plasma v: 6.3.4 tk: Qt v: N/A info: frameworks v: 6.13.0
    wm: kwin_wayland vt: 1 dm: SDDM Distro: EndeavourOS base: Arch Linux
Machine:
  Type: Laptop System: HP product: HP EliteBook 850 G6 v: SBKPF
    serial: <superuser required> Chassis: type: 10 serial: <superuser required>
  Mobo: HP model: 8549 v: KBC Version 52.6F.00 serial: <superuser required>
    part-nu: 6XD79EA#ABH uuid: <superuser required> UEFI: HP
    v: R70 Ver. 01.28.00 date: 04/12/2024
Battery:
  ID-1: BAT0 charge: 6.1 Wh (15.6%) condition: 39.0/56.3 Wh (69.3%)
    volts: 10.2 min: 11.6 model: Hewlett-Packard Primary type: Li-ion
    serial: <filter> status: discharging cycles: 267
CPU:
  Info: model: Intel Core i5-8265U bits: 64 type: MT MCP
    arch: Comet/Whiskey Lake note: check gen: core 8 level: v3 note: check
    built: 2018 process: Intel 14nm family: 6 model-id: 0x8E (142)
    stepping: 0xC (12) microcode: 0xFC
  Topology: cpus: 1x dies: 1 clusters: 4 cores: 4 threads: 8 tpc: 2
    smt: enabled cache: L1: 256 KiB desc: d-4x32 KiB; i-4x32 KiB L2: 1024 KiB
    desc: 4x256 KiB L3: 6 MiB desc: 1x6 MiB
  Speed (MHz): avg: 2403 min/max: 400/3900 scaling: driver: intel_pstate
    governor: powersave cores: 1: 2403 2: 2403 3: 2403 4: 2403 5: 2403 6: 2403
    7: 2403 8: 2403 bogomips: 28800
  Flags: avx avx2 ht lm nx pae sse sse2 sse3 sse4_1 sse4_2 ssse3 vmx
  Vulnerabilities:
  Type: gather_data_sampling mitigation: Microcode
  Type: ghostwrite status: Not affected
  Type: itlb_multihit status: KVM: Split huge pages
  Type: l1tf status: Not affected
  Type: mds status: Not affected
  Type: meltdown status: Not affected
  Type: mmio_stale_data mitigation: Clear CPU buffers; SMT vulnerable
  Type: reg_file_data_sampling status: Not affected
  Type: retbleed mitigation: Enhanced IBRS
  Type: spec_rstack_overflow status: Not affected
  Type: spec_store_bypass mitigation: Speculative Store Bypass disabled via
    prctl
  Type: spectre_v1 mitigation: usercopy/swapgs barriers and __user pointer
    sanitization
  Type: spectre_v2 mitigation: Enhanced / Automatic IBRS; IBPB:
    conditional; RSB filling; PBRSB-eIBRS: SW sequence; BHI: SW loop, KVM: SW
    loop
  Type: srbds mitigation: Microcode
  Type: tsx_async_abort status: Not affected
Graphics:
  Device-1: Intel WhiskeyLake-U GT2 [UHD Graphics 620] vendor: Hewlett-Packard
    driver: i915 v: kernel arch: Gen-9.5 process: Intel 14nm built: 2016-20
    ports: active: eDP-1 empty: DP-1, DP-2, HDMI-A-1, HDMI-A-2 bus-ID: 00:02.0
    chip-ID: 8086:3ea0 class-ID: 0300
  Device-2: Quanta HP HD Camera driver: uvcvideo type: USB rev: 2.0
    speed: 480 Mb/s lanes: 1 mode: 2.0 bus-ID: 1-9:5 chip-ID: 0408:5373
    class-ID: 0e02 serial: <filter>
  Display: wayland server: X.org v: 1.21.1.16 with: Xwayland v: 24.1.6
    compositor: kwin_wayland driver: X: loaded: modesetting
    alternate: fbdev,intel,vesa dri: iris gpu: i915 display-ID: 0
  Monitor-1: eDP-1 model: AU Optronics 0x21ed built: 2018 res:
    mode: 1920x1080 hz: 60 scale: 125% (1.25) to: 1536x864 dpi: 142 gamma: 1.2
    size: 344x194mm (13.54x7.64") diag: 395mm (15.5") ratio: 16:9
    modes: 1920x1080
  API: EGL v: 1.5 hw: drv: intel iris platforms: device: 0 drv: iris
    device: 1 drv: swrast gbm: drv: iris surfaceless: drv: iris wayland:
    drv: iris x11: drv: iris
  API: OpenGL v: 4.6 compat-v: 4.5 vendor: intel mesa v: 25.0.5-arch1.1
    glx-v: 1.4 direct-render: yes renderer: Mesa Intel UHD Graphics 620 (WHL
    GT2) device-ID: 8086:3ea0 memory: 7.53 GiB unified: yes display-ID: :1.0
  API: Vulkan v: 1.4.309 layers: 4 device: 0 type: integrated-gpu name: Intel
    UHD Graphics 620 (WHL GT2) driver: mesa intel v: 25.0.5-arch1.1
    device-ID: 8086:3ea0 surfaces: xcb,xlib,wayland
  Info: Tools: api: clinfo, eglinfo, glxinfo, vulkaninfo
    de: kscreen-console,kscreen-doctor wl: wayland-info
    x11: xdpyinfo, xprop, xrandr
Audio:
  Device-1: Intel Cannon Point-LP High Definition Audio
    vendor: Hewlett-Packard driver: sof-audio-pci-intel-cnl
    alternate: snd_hda_intel, snd_soc_avs, snd_sof_pci_intel_cnl
    bus-ID: 00:1f.3 chip-ID: 8086:9dc8 class-ID: 0401
  Device-2: Focusrite-Novation Scarlett Solo USB driver: snd-usb-audio
    type: USB rev: 2.0 speed: 480 Mb/s lanes: 1 mode: 2.0 bus-ID: 1-2:2
    chip-ID: 1235:801c class-ID: fe01
  API: ALSA v: k6.14.4-arch1-2 status: kernel-api
    tools: alsactl,alsamixer,amixer
  Server-1: PipeWire v: 1.4.2 status: active with: 1: pipewire-pulse
    status: active 2: wireplumber status: active 3: pipewire-alsa type: plugin
    4: pw-jack type: plugin tools: pactl,pw-cat,pw-cli,wpctl
Network:
  Device-1: Intel Ethernet I219-V vendor: Hewlett-Packard driver: e1000e
    v: kernel port: N/A bus-ID: 00:1f.6 chip-ID: 8086:15be class-ID: 0200
  IF: enp0s31f6 state: down mac: <filter>
  Device-2: Intel Wi-Fi 6 AX200 driver: iwlwifi v: kernel pcie: gen: 2
    speed: 5 GT/s lanes: 1 bus-ID: 3a:00.0 chip-ID: 8086:2723 class-ID: 0280
  IF: wlan0 state: up mac: <filter>
  Info: services: NetworkManager, systemd-timesyncd, wpa_supplicant
Bluetooth:
  Device-1: Intel AX200 Bluetooth driver: btusb v: 0.8 type: USB rev: 2.0
    speed: 12 Mb/s lanes: 1 mode: 1.1 bus-ID: 1-10:6 chip-ID: 8087:0029
    class-ID: e001
  Report: btmgmt ID: hci0 rfk-id: 0 state: up address: <filter> bt-v: 5.2
    lmp-v: 11 status: discoverable: no pairing: no class-ID: 6c010c
Drives:
  Local Storage: total: 238.47 GiB used: 93.9 GiB (39.4%)
  SMART Message: Unable to run smartctl. Root privileges required.
  ID-1: /dev/nvme0n1 maj-min: 259:0 vendor: KIOXIA model: N/A
    size: 238.47 GiB block-size: physical: 512 B logical: 512 B speed: 31.6 Gb/s
    lanes: 4 tech: SSD serial: <filter> fw-rev: AGHA4101 temp: 23.9 C
    scheme: GPT
Partition:
  ID-1: / raw-size: 220.49 GiB size: 215.97 GiB (97.95%)
    used: 93.67 GiB (43.4%) fs: ext4 dev: /dev/nvme0n1p2 maj-min: 259:2
Swap:
  Kernel: swappiness: 60 (default) cache-pressure: 100 (default) zswap: yes
    compressor: zstd max-pool: 20%
  ID-1: swap-1 type: partition size: 16.98 GiB used: 0 KiB (0.0%)
    priority: -2 dev: /dev/nvme0n1p3 maj-min: 259:3
Sensors:
  System Temperatures: cpu: 35.0 C pch: 28.0 C mobo: N/A
  Fan Speeds (rpm): N/A
Info:
  Memory: total: 16 GiB note: est. available: 15.43 GiB used: 2.44 GiB (15.8%)
  Processes: 233 Power: uptime: 11m states: freeze,mem,disk suspend: deep
    avail: s2idle wakeups: 0 hibernate: platform avail: shutdown, reboot,
    suspend, test_resume image: 6.16 GiB services: org_kde_powerdevil,
    power-profiles-daemon, upowerd Init: systemd v: 257 default: graphical
    tool: systemctl
  Packages: 1467 pm: pacman pkgs: 1449 libs: 490 tools: yay pm: flatpak
    pkgs: 18 Compilers: gcc: 15.1.1 Shell: Bash v: 5.2.37 running-in: konsole
    inxi: 3.3.38

pacman -Qs alsa

local/alsa-card-profiles 1:1.4.2-1
    Low-latency audio/video router and processor - ALSA card profiles
local/alsa-firmware 1.2.4-4
    Firmware binaries for loader programs in alsa-tools and hotplug firmware loader
local/alsa-lib 1.2.14-1
    An alternative implementation of Linux sound support
local/alsa-plugins 1:1.2.12-4
    Additional ALSA plugins
local/alsa-tools 1.2.14-1
    Advanced tools for certain sound cards
local/alsa-topology-conf 1.2.5.1-4
    ALSA topology configuration files
local/alsa-ucm-conf 1.2.14-2
    ALSA Use Case Manager configuration (and topologies)
local/alsa-utils 1.2.14-1
    Advanced Linux Sound Architecture - Utilities
local/lib32-alsa-lib 1.2.14-1
    An alternative implementation of Linux sound support (32 bit)
local/lib32-alsa-plugins 1.2.12-1
    Additional ALSA plugins (32-bit)
local/pipewire-alsa 1:1.4.2-1

pacman -Qs pulse

local/lib32-libcanberra 1:0.30+r2+gc0620e4-3
    A small and lightweight implementation of the XDG Sound Theme Specification (32-bit)
local/lib32-libpulse 17.0+r43+g3e2bb8a1e-1
    A featureful, general-purpose sound server (32-bit client libraries)
local/libcanberra 1:0.30+r2+gc0620e4-4
    A small and lightweight implementation of the XDG Sound Theme Specification
local/libpulse 17.0+r43+g3e2bb8a1e-1
    A featureful, general-purpose sound server (client library)
local/pavucontrol 1:6.1-1
    PulseAudio Volume Control
local/pipewire-pulse 1:1.4.2-1
    Low-latency audio/video router and processor - PulseAudio replacement
local/plasma-pa 6.3.4-1 (plasma)
    Plasma applet for audio volume management using PulseAudio
local/pulseaudio-qt 1.7.0-1
    Qt bindings for libpulse

pacman -Qs pipewire

local/easyeffects 7.2.3-2
    Audio Effects for Pipewire applications
local/gst-plugin-pipewire 1:1.4.2-1
    Multimedia graph framework - pipewire plugin
local/kpipewire 6.3.4-1 (plasma)
    Components relating to pipewire use in Plasma
local/lib32-libpipewire 1:1.4.2-1
    Low-latency audio/video router and processor - 32-bit - client library
local/lib32-pipewire 1:1.4.2-1
    Low-latency audio/video router and processor - 32-bit
local/libpipewire 1:1.4.2-1
    Low-latency audio/video router and processor - client library
local/libwireplumber 0.5.8-1
    Session / policy manager implementation for PipeWire - client library
local/pipewire 1:1.4.2-1
    Low-latency audio/video router and processor
local/pipewire-alsa 1:1.4.2-1
    Low-latency audio/video router and processor - ALSA configuration
local/pipewire-audio 1:1.4.2-1
    Low-latency audio/video router and processor - Audio support
local/pipewire-jack 1:1.4.2-1
    Low-latency audio/video router and processor - JACK replacement
local/pipewire-pulse 1:1.4.2-1
    Low-latency audio/video router and processor - PulseAudio replacement
local/qpwgraph 0.9.0-1 (pro-audio)
    PipeWire Graph Qt GUI Interface
local/wireplumber 0.5.8-1

The way I understand it, this is how ALSA supposedly always works (hogging the audio streams) and JACK should be used if you’re planning on having multiple audio streams at the same time.

The problem here is that JACK works very well in Reaper, but will play back the very same audio file about 15db more quietly than ALSA does.

I’ve currently registered (waiting for approval) an account over at the Cockos forum (Reaper devs) because this 15db volume difference only happens in Reaper.
I’d prefer to use JACK as well on this laptop, as I also use it for Reaper on my desktop, but the 15db volume difference was a real showstopper, until ALSA currently decided to also give up.

have you checked with

wpctl status

unless you are using only alsa , it should be pipewire , that had pipewire-jack for back-end

wpctl status

PipeWire 'pipewire-0' [1.4.2, lesd@les-hpelitebook850g6, cookie:1960895785]
 └─ Clients:
        32. WirePlumber                         [1.4.2, lesd@les-hpelitebook850g6, pid:961]
        33. pipewire                            [1.4.2, lesd@les-hpelitebook850g6, pid:963]
        46. WirePlumber [export]                [1.4.2, lesd@les-hpelitebook850g6, pid:961]
        79. kwin_wayland                        [1.4.2, lesd@les-hpelitebook850g6, pid:1007]
        82. libcanberra                         [1.4.2, lesd@les-hpelitebook850g6, pid:1142]
        83.                                     [1.4.2, lesd@les-hpelitebook850g6, pid:1142]
        84. xdg-desktop-portal                  [1.4.2, lesd@les-hpelitebook850g6, pid:1014]
        85. libcanberra                         [1.4.2, lesd@les-hpelitebook850g6, pid:1177]
        86. plasmashell                         [1.4.2, lesd@les-hpelitebook850g6, pid:1177]
        87.                                     [1.4.2, lesd@les-hpelitebook850g6, pid:1177]
        89. wpctl                               [1.4.2, lesd@les-hpelitebook850g6, pid:1734]

Audio
 ├─ Devices:
 │      50. Cannon Point-LP High Definition Audio Controller [alsa]
 │
 ├─ Sinks:
 │      56. Cannon Point-LP High Definition Audio Controller HDMI / DisplayPort 3 Output [vol: 1.00]
 │      57. Cannon Point-LP High Definition Audio Controller HDMI / DisplayPort 2 Output [vol: 1.00]
 │      58. Cannon Point-LP High Definition Audio Controller HDMI / DisplayPort 1 Output [vol: 1.00]
 │  *   59. Cannon Point-LP High Definition Audio Controller Speaker [vol: 0.52]
 │
 ├─ Sources:
 │      60. Cannon Point-LP High Definition Audio Controller Stereo Microphone [vol: 1.00]
 │  *   61. Cannon Point-LP High Definition Audio Controller Digital Microphone [vol: 0.54]
 │
 ├─ Filters:
 │
 └─ Streams:

Video
 ├─ Devices:
 │      51. HP HD Camera                        [v4l2]
 │      52. HP HD Camera                        [v4l2]
 │
 ├─ Sinks:
 │
 ├─ Sources:
 │  *   80. HP HD Camera (V4L2)
 │
 ├─ Filters:
 │
 └─ Streams:

Settings
 └─ Default Configured Devices:
         0. Audio/Sink    alsa_output.usb-Focusrite_Scarlett_Solo_USB-00.HiFi__Line1__sink
         1. Audio/Source  alsa_input.usb-Focusrite_Scarlett_Solo_USB-00.HiFi__Mic2__source

I was able to reproduce the ALSA behaviour on my desktop (where only ALSA works within Reaper and all audio streams outside of that (Youtube videos, local music files) will not work at all.
I believe this is how ALSA usually is supposed to function.

However, on my desktop, there is no volume difference between using ALSA or JACK in Reaper.