I added lines that were in modules.conf to modprobe.conf. Now and mpu401 driven devices is active! The USB still is not, though snd-usb-audio is registering on boot and deregistering on shutdown. Both are listed in lsmod, similar to listing in 2.4.22: # lsmod | grep mpu401 snd_mpu401 4224 0 snd_mpu401_uart 8352 2 snd_mpu401,snd_es1968 snd_rawmidi 25536 2 snd_usb_audio,snd_mpu401_uart snd 55012 10 snd_mixer_oss,snd_mpu401,snd_usb_audio,snd_es19 68,snd_ac97_codec,snd_pcm,snd_timer,snd_mpu401_uart,snd_rawmidi,snd_seq_device # lsmod | grep usb snd_usb_audio 63968 0 usbcore 114652 1 snd_usb_audio snd_pcm 104640 2 snd_usb_audio,snd_es1968 snd_rawmidi 25536 2 snd_usb_audio,snd_mpu401_uart snd 55012 10 snd_mixer_oss,snd_mpu401,snd_usb_audio,snd_es19 68,snd_ac97_codec,snd_pcm,snd_timer,snd_mpu401_uart,snd_rawmidi,snd_seq_device # lsmod | grep es1968 snd_es1968 34020 0 snd_ac97_codec 55556 1 snd_es1968 snd_pcm 104640 2 snd_usb_audio,snd_es1968 snd_page_alloc 12100 2 snd_es1968,snd_pcm snd_mpu401_uart 8352 2 snd_mpu401,snd_es1968 snd 55012 10 snd_mixer_oss,snd_mpu401,snd_usb_audio,snd_es1968,snd_ac97_codec,snd_pcm,snd_timer,snd_mpu401_uart,snd_rawmidi,snd_seq_device The snd-es1968 and snd_ac97_codec are similarly listed, even though this card is also not active (the card has a AGOPO chip but different codecand there is presently no ALSA driver for it). Only the mpu401 is listed in cat /proc/asound/cards. Both the mpu401 and the USB interface worked in 2.4.22.